Announcement

**Lago Blue** · 7 September 2018, 17:51

Recent forum member customer comment on the Arm-Stops mod alone:

" Impression on driving are; wow! What a difference. I’d say it corners more like my B6 Passat than a B3 coupe! Turn in is so precise and composed. And tightening the steering into a corner actually encourages the car to turn harder, whereas normally the front starts progressively understeering the more you turn in during a corner. And of course a notable difference in the noise levels. And the composure under breaking is a step change too. Very impressed with your mod my friend – chuffed to bits "

...and on both the Arm-Stops and Strut-Stops mods together:

"The 2 mods combined have transformed the way the car feels. "

**Lago Blue** · 8 December 2018, 04:41

Wanted: Trade Agreement to Conclude in 2019.

Change is rampant. Markets may roil, leaders obfuscate and old alliances are questioned, but at least your A-arm bushings need not become degraded so quickly. This mod will keep your A-arms positively sprung to a centered position between the sub-frame brackets long-term, something the stock arrangement does only briefly when brand new.

Having had favourable feed-back during the past 3 yrs. these have been on offer, I'd like to know if I up the ante on these can I attract someone to test these slightly more heavily? I'm looking for independent track-day, ice-racing or rally testing of this add-on suspension product for use on a dual-purpose street-licensed car.

As the current driving season closes down and you are considering what maintenance you will do over the winter, this asks you to consider replacing your A-arm bushings; and at the same time reinforcing them with "Arm-Stops" to extend bushing life and improve the driving experience over the stock arrangement.

This product and this particular ask might appeal to someone who either currently runs OEM A-arm bushings that would require replacement in any case and would like to keep running OEMs, or who is not entirely satisfied with what their poly bushings provide, or perhaps even to someone who is also considering whether to switch to polyurethane; or not.

What I'd like to have happen is for someone to run these widgets next year in both domains (on-road and off) and write up their experience with and impressions of them, good or bad, in both realms, here on the forum (including some event photos please!). Not wanting to be accuse-able of skewing the results, I think I must keep my offer quite modest; I will refund your postage costs. That's it.

So basically three separate opportunities, one on ice, one on gravel and one on track, to make or break publicly, these so far street successful aids for OEM bushings, recover an admittedly small inducement in any case; and perhaps enjoy any benefits these items (an easily reversable mod) might provide.

For your consideration, gentlemen.

**Lago Blue** · 19 October 2019, 19:07

Arm-Stops enroute to Estonia for fit and operational testing with Kiku's lovely fab'd A-arms and Meyle HD bushings.

This is an experiment as Arm-Stops are sized specifically to fit and proven to reinforce the usually Audi dealer-sourced Boge bushings, but the Meyle HD's may be similar enough.

https://www.s2forum.com/forum/member...ular-wishbones

https://media.carparts-cat.com/pdf/E...04-2005_en.pdf

Time will tell.

**Lago Blue** · 24 January 2020, 03:19

Stop the A-arm's race to the rear under braking;

Prevent the noise non-OEMs could be making.

With Audi / Boges and Arm-Stops, steering response is tops,

And you'll save what other choices are taking.

**Lago Blue** · 22 February 2020, 17:17

Tired of this Spring maintenance ritual? Bend demand-side economics to your favour, and net a most inexpensive handling advantage...

By simply altering the job-description of exactly what the A-arm bushes have to do, we protect their as-new original inherent strength and integrity, allowing that undiminished full capacity to only have to resist the more minor bending, twist and radial loads, and also greatly extend their service-life. This benefit will be felt during cornering and braking. Pairs nicely with Strut-Stops. Ounces of prevention netting £'s of cure.

This contends that without this mod, even your recently replaced bushings have again been marked for early failure, as follows:

1) Bending. On quite late removal, your damaged bushing's central metal cores are often found torn loose and / or to have been pointing somewhat off of parallel from the car' s center-line. This permanent damage and deformation resembles what happens under what is called cardanic loading (illustration below). One can imagine how this has shifted your ball-joints' positions, altering your alignment; and the cores' looseness has allowed the bottoms of the two MacPherson struts to move (i.e.: to both wander and be pushed around) somewhat un-tethered and independently, particularly under braking and cornering. However, despite these real effects, this contends that they are not due to bending loads alone, but are symptoms of greater forces at work, and are entirely preventable.

Cardanic load acting on bushing.png(illustrations by Dietrich Teigler Nachf. GmbH & Co. KG)

2) Twist. The beauty of the original design is in its simple reliability due to a lack of moving parts, resilient and quiet response, sealed construction and near friction-less operation. When installed exactly as per the factory instruction, they are at least briefly, fully capable of providing a perfect hinge-point, resisting the torsional loading and unloading (illustration below) of full suspension travel, without being degraded. Key to that performance is the small angular change required to accommodate full travel, and the good condition of the bush's bonded rubber / steel interfaces. Again, this contends that core damage seen which resembles failure from twist, is in fact not from twist alone or even twist plus bending.

Torsional load acting on bushing.png

3) Lateral shift. Our bushing's greatest strength is in its' ability to resist radial loads (illustration below) and if kept as-new, it can continue to respond meaningfully to multi-G steering and cornering inputs without degradation if not indefinitely, certainly for many years. As above, this asserts even a total failure of strictly the bonding between the steel interior and a rubber core's outer surface found perfectly intact, is not a symptom of lateral forces alone or even this not inconsiderable load plus twist and bending, but is (with the mod) entirely preventable.

Radial load acting on bushing.png

4) Long-axis displacement. This bushing's weakest flank, along its' center-line axis, is also precisely where its' highest loads are delivered to (illustration below). It is this vulnerability to damage from high peak axial loads that begins the certain and familiar break-down process of the bushings. Peak loads are seen primarily under braking (but also at the far edge of pot-holes; and when one cranks on a good deal of rack-travel with the engine on and the tires not rolling), loads which are by far, greater than any other single load type above. By eliminating this one task (with the subject mod), this highest load against their weakest flank, from the bushes' above list of jobs they must do, we keep both the original integrity of the bushes' construction, and their strength; fully intact. That preserved capability to respond, better resists the now also abbreviated above task list, giving us both a better driving response and a much longer service-life.

Axial load acting on bushing.png

5) Fifth-order loading. Because this axial-loading (illustration above) is so powerful and so frequent, it dwarfs anything from the first three types described above, however what really accelerates the over-load of the stock installations, is when the bushes have to deal with any of those first three, either singly or in combination; plus axial. Perhaps one of the easiest examples to visualize, of this combi-type of bushing over-load to the stock bushing installation, occurs under heavy braking; when the nose then also dives.

Unfortunately, in the stock arrangement, it is axial loads which stress the cores fore and aft constantly, during almost every moment of every-day driving (save for briefly during gear-chages). It is all these axial loads that with this mod; are transferred elsewhere; by-passing the cores.

By therefore eliminating (with the subject mod) all those "plus axial" loading situations including the preceding (and consider that with the mod, the highest both pure 4th and these 5th combi-type loads are all now prevented), the net stress to the bushes is thus kept much farther under their peak elastic limit than otherwise, while also keeping their capacity to carry load, near to their as-new condition. Their now reduced task-list also means a much reduced energy through-put, allowing them to run much cooler. They therefore do not succumb to the usual self-destruction and permanent deformation enroute to early failure, otherwise seen. No alteration to any of the original parts are required. Removal of the mod would immediately restore the stock condition. I don't believe there is any down-side to this mod; except in not doing it.

**Lago Blue** · 1 July 2020, 03:04

7 Reasons to consider Arm-Stops…

- Arm-Stops are a simple way to modify how OEM A-arm bushings function, to obtain stronger and longer service lives from the installed A-arms’ inner hinge-lines, reduced maintenance costs and other driving-dynamics’ benefits.

- Arm-Stops prevent your A-arms, brakes and normal every-day driving from quickly degrading your necessarily next set of new OEM A-arm bushings.

- Arm-Stops enable improved stability and steering response via A-arms held more durably and steadfastly still (on their fore-aft axis); than what the stock arrangement alone can provide.

- Arm-Stops will keep stock bushings nearer to new condition years longer than the stock install, comfortable and quiet yet more load-capable than stock, better dynamic holding of alignment settings, even providing them some protection from pot-hole strikes.

- Arm-Stops provide a empirically-proven low-friction method for the reinforced attachment of A-arms to the sub-frame, and ought to be considered foundational to most other suspension, brake freshening and hardware improvements.

- Arm-Stops, despite being a much older, evolved and an equally effective mod than Strut-Stops, it remains less popular. It certainly pairs very well with the newer but more widely-followed Strut-Stops (for OEM top-mounts) to provide more complete, stable, precise and better mirrored (LH to RH) two-strut axis station-keeping while underway. However, despite lower cost and greater simplicity than Strut-Stops, too often, Arm-Stops (which better secure the bottom of the strut), this logical other half of improved steering-axis control; remains largely unimplemented; except by a happy few.

- Arm-stops may be, not just the cheapest chassis mod ever, they may also have the best cost / benefit ratio. So perhaps a truly most economical mod?

**Lago Blue** · 23 January 2021, 07:59

How Neglected A-arm Bushing's Contribute to a Lack of Steering Precision; and a Suggested Better Than Stock Fix...

(...or While your attention was elsewhere, these bushes went ‘off’; and why you may want to fix that.)

Here are some excerpts from a couple of automotive textbooks, a bushing manufacturers catalog, a university lecture and a couple of research papers which may help to explain the perceived effect of Arm-Stops added to our stock steering system's condition. Because the issues that Arm-Stops address are not unique to our cars, it should not be surprising that others have both detected and written about these same types of deficiencies; elsewhere. Additionally, because the A-arm bushings are perhaps not usually thought of as central to our steering system's performance, I will try to outline that contention here also.

In my view, the direction one needs to go in to improve our stock steering response is precisely this:

'The steering train must be highly rigid.'

(from: Automotive Engineering, Part 1 Basics of Vehicle Construction, Steering system Requirements. Stjepan Galambos, Department for Mechanization and Design Engineering, Chair for Engines and Vehicles, U of Novi Sad, Serbia.)

Certainly this succinct and simple requirement best needs to be applied to our entire linkage 'train' in order to improve steering response. That entirety must also include the fulcrums around which the front wheels are leveraged to change direction; and in particular, the sturdiness with which those pivot-points are held still. I refer here to the A-arm bushes where a good deal of slack develops in the mechanical train that can with this mod, easily be eliminated; and prevented from reoccurring for a very long time.

When the typical stock condition is viewed from under the safely parked car, steering inputs can be seen to be forcing the A-arms, one goes forwards and the other backwards simultaneously, if the rack is repeatedly cycled left and right. That fore/aft motion is also lost steering signal between you and the front wheels. That slack has to be first taken up before every reversal in steering train throughput, and before every directional change of steering-wheel rotation that you make; has any effect. Additionally, because this issue occurs independently between each wheel and the rack, while underway, at any given moment neither wheel need be exactly where the rack is asking each to point, nor do the two tires need agree as to where to point. Therefore the self-centering and on-centre feel of the steering is diminished.

These conditions allow each wheel to constantly and independently drift slightly in and out of their design positions, they will be pushed about directionally as neither is full-time properly constrained by the entire steering train. They can and will wander, each about their steering axis between the ends of the available slack in the train, directed within that slack range by the road; rather than the driver.

This type of clearance often goes undetected as the driver may not notice the insidious onset of its effects, which may develop slowly over time, and it doesn’t show up when your car undergoes a proper alignment either, because only the static settings are examined. This slack (which only becomes apparent when you add changing loads to the steering system), usually and literally only comes into play; when the car is moving.

Your perhaps more likely than not, worn and torn bushings are the only means by which the A-arms may yet self-center (in the fore to aft sense) in their mountings, to hold the base of the two steering axis still, if at all. What this serves to illustrate is that while underway, forces across the contact-patches are controlling your instantaneous alignment, not the other way around, so the very smallest of signals sent and received by the driver are mixed and or missing, as each wheel does in a very small way; its own random thing. The precise aim of Arm-Stops is to turn that situation around.

Those of you with an early car, which mirrors this same A-arm mounting design at the rear, might recognize that this same issue could be occurring there also; and be correct.

The flow chart below tellingly includes elasticity (2nd item) as a known issue in the complex driver to front wheel's contact-patches control-loop:

(This flow-chart and the slide below are from: euromotor.org part of their online course Automotive Engineering II)

image_80583.png

This next slide, in its list of demands on the steering system under ‘Sensitivity’ also emphasizes the basic need for zero play by stating ‘-> no clearance’ after outlining the reason why - ‘distinct realization of the steering wheel angle’. Yes, what is being discussed here are very small changes to the steering system; and to how it functions; to yield subtle but invaluable improvements.

Demands on the Steering System Screen Shot 2021-01-10 at 21.37.13 copy.png

On the question of steering ‘feel’ (outlined to some small degree in the two previous slides), here is a compelling explanation of why we should want to improve this characyeristic: (I’ve edited this for brevity from: The Multi-body Systems Approach to Vehicle Dynamics (Second Edition), 2015 by Mike Blundell, Damian Harty)

7.5 Steering feel as a subjective modifier.
Impressions of vehicle behaviour are gathered to a significant extent through the hand-wheel, whether consciously or subconsciously. A great deal of effort is concentrated in modern road cars on the manner in which torque is transmitted back to the driver up the steering column. Those skilled in the art have no difficulty distinguishing between steering issues and vehicle issues. However, a lack of clarity can lead to confusion if steer effects are not separated from vehicle effects.

Steering feel is correctly given a great deal of importance in road car design since it is the primary means by which the driver comprehends the dynamics of the vehicle. Changes in steering torque are a primary input for skilled drivers to detect vehicle behaviour. A common description of ‘steering feel’ involves discussion of tyre aligning torques. When driving normally, the tyres generate forces by distortions in the contact patch that result in a moment attempting to return the tyre to a zero slip angle condition. If the steering system is well designed, it is delivered with very little corruption from vehicle weight and frictional effects directly to the hands of the driver.

In addition, if a vehicle starts to spin then the steering system informs the driver within around 0.1 seconds using the ‘castoring’ torque generated by operating the entire vehicle at a large slip angle. This mechanism ensures minimum hand-wheel torque when the wheels are placed so as to recover the skid; in this way the steering system fairly directly, signals the current body slip angle to the driver. Skilled drivers are extremely sensitive to these messages, which arrive ahead of the brain's processing of the results of its data from the inner ear and significantly ahead of messages decoded purely from the visual environment.

It can be seen that steering systems that mask any or all of these mechanisms might be less helpful than steering systems that do not. Therefore it is suggested that proposing metrics to capture these aspects of the steering system and examining design variables that influence them will lead to well-behaved steering systems even without extensive prototyping and subjective test activities.

Just my thought on the above, the authors are almost describing a kind of mental/physical flow-state of driving. In my mind this comes more easily to me on a bicycle or motor-bike (perhaps because they are more like skiing or flying), but when it does happen, that the vehicle is a separate thing from me - disappears, and I could believe that the car is just an extension of my thoughts. And on a good day with my Audi; it happens.

Graph (below) of steering elasticity plus text paragraph for Fig 3.99.
(From: The Automotive Chassis Fundamentals, 2nd Ed., by Jörnsen Reimpell, Helmut Stoll, Jürgen W. Betzler)

Of note here: The true steering ratio, as experienced by the driver, would be the dynamic ratio, this comprises the proportions resulting from the rigid steering (the static gear ratio) and the elastic (which has its effects while underway and subtracts from (but adds numerically to) the static gear ratio)(see Fig. 3.99) portion.

Dynamic Stering Ratio graph shows train elasticity Fig 3.99 Screen Shot 2021-01-18 at 23.35.24.png

Dynamic Steering Ratio text for Fig 3.99. Screen Shot 2021-01-18 at 23.36.43.png

Ideally we would want the above two curves above to lay one on top of one the other, which would indicate zero elasticity in our train.

When the elasticity of new gives way to unrestrained slack (as the bushings degrade further) in the steering train, what occurs during those intervals when slack is being traversed through, or being taken up towards zero (as must happen in order to effect every direction change), is that no signal is transmitted to the individual wheels themselves or to the hand-wheel and driver either, because the steering is effectively disconnected during those; yes brief but vacant times.

The table below from a bush manufacturer's catalog shows measured typical bushing strength values, note both the radial stiffness (quite strong) and respective axial values (relatively weak) in any example.

Trellborg (Sweden) table:
Bushing stiffness on 3 axis drwg and table Screen Shot 2021-01-14 at 10.35.35.png

The graph (below) is interesting for a couple of reasons. Engineers spend a great deal of time (too much time in my view) figuring how to figure how strong a bushing will be, without actually making and measuring said bushing performance (and not enough time doing fatigue analysis!).

This graph does look briefly at bushing failure (bonding failure, where the elastomer separates from the steel core and/or shell, with which you might be familiar).

Although a little hard to see at first, this graph has 3 sets of curves, one set each for radial, axial and torsional stiffness, the solid lines are calculated amounts, the dotted lines are measured ones. Again note how much stronger a given bush is radially vs axially. Perhaps most interesting for our purposes here was how this also illustrates that although making a bushing longer does make it stronger radially (to a point), it does not make it stronger axially.

U de Monterrey graph (below) of radial, axial and torsional bush strength:

(from: Analytical Design and Optimization of an Automotive Rubber Bushing
Jonathan Rivas-Torres 1, Juan C. Tudon-Martinez 1, Jorge de-J. Lozoya-Santos 2, Ricardo A. Ramirez-Mendoza 2, and Andrea Spaggiari 3.
1 Universidad de Monterrey, Ignacio Morones Prieto 4500, Jesús M. Garza, 66238 San Pedro Garza García, NL, Mexico
2 Tecnológico de Monterrey, Av. E. Garza Sada, Col. Tecnológico, 64849 Monterrey, NL, Mexico
3 Università degli Studi di Modena e Reggio Emilia, Via Giovanni Amendola, 2, 42122 Reggio Emilia, Italy. Academic Editor: Jussi Sopanen Published 26 Mar 2019)

Bushing stiffness 3 axis comparison Screen Shot 2021-01-14 at 09.40.11.png

The graph below compares typical bushing radial strength to axial at various displacement distances (i.e.: compliance). Note again how weak it is in the axial (fore/aft direction) vs the radial (lateral direction) stiffness.

(From: Evaluation of Bushing Dissipation Rates and Component Flexibility in the Dynamic Analysis of the DN101 Lower control Arm Mounted on Nonlinear Elastic Bushings
Ragnar Ledesma Centre for Automotive Structural Durability Simulation The University of Michigan 2216 G.G. Brown Ann Arbor, MI 48 109-2125)

U of Michigan graph of bush displacement (or compliance) vs force, radially and axially:

LCA bushing, stiffness and displacement, radial and axial. From U of Mich study Screen Shot 2021-01-13 at 21.03.31.png

My point in including the above two items is to illustrate that, as they are closest to the tire's contact-patches, most of the fore / aft forces (perhaps 2/3rds(?) (and for later on in this discussion, I do think that must cause some bush heating), both braking and propulsion, and obstacle impact loads (the remainder (1/3rd or so(?) of fore/aft forces) go through the top-mounts) are felt continuously along what is by far the weakest flank (as shown above) of the A-arm bushes, along their through-bolt axis (parallel to the chassis fore / aft axis) and that is why they quickly degrade. Arm-Stops, by changing how those loads are routed to and from the chassis, relieves the bush elastomers and their bonded interfaces of that task entirely, extending their service lives markedly and at the same time fixing still, nigh on perfectly while underway, the bottom of the MacP. strut. Hence, with the bottom of the steering axis held steady, the above slack is eliminated; and thereby improving the stock steering condition.

My purpose in including the following four graphs is to illustrate the relative speed (indicated by time) and magnitude of forces at work against these bushes, not that these are specifically for our cars, but that they may serve as indicators of the general order of magnitude that we might expect to find in our cases, and to show why in the stock un-aided arrangement, our axially weak bushes are so easily defeated by these significant forces.

U of Michigan graph of ball-joint displacement during test-track derived simulated pot-hole event (looks like about a 50mm deep ‘hole’):

LCA ball-joint vert dsplcmnt at P-hole from U of Mich study Screen Shot 2021-01-13 at 21.06.18.png

The graph below illustrates the force (note the amount of Newtons reached during the 1st and 2nd peaks) with which the ball-joint is first forced aft (amount below the zero line) during the above pot-hole event.

LCA ball-joint, force seen at, along fore aft diresction at P-hole from U of Mich study Screen Shot 2021-01-13 at 21.04.29.png

The graph below illustrates the distance the above ball-joint is at first forced aft (distance below the Zero line) during that pot-hole event. In our case it is this most severe fore / aft movement during this type of event that causes the most rapid breakdown of the internal bonding between the elastomer and its steel shell and core. However even with the less extreme drama of everyday driving, the same fate too soon befalls all our un-aided bushes.

BJ Displacement fore aft Screen Shot 2021-01-22 at 23.32.36.png

Surprising to me was the amount of lateral force also generated by this same pot-hole strike (despite that it was hit while moving straight forward). This speaks to the large forces at work here and that simple heating of the bushes (due to the constant energy input these bushes must endure everyday, even without singularities such as this), is most certainly a part of why they, if left stock; fail early:

LCA ball-joint, lat force force seen at, at P-hole from U of Mich study Screen Shot 2021-01-13 at 21.06.02.png

Concluding remarks:
In our case, because a good deal of the elasticity found in our steering system occurs due to the fore/aft compliance of the A-arm bushings, and that the Arm-Stops mod, by fencing fore/aft A-arm travel, precludes same; the expected result would be a more responsive steering linkage 'train'. Thus the perception of more precise steering; post mod.

If you’ve followed along thus far, two take-aways from this might be a) if you supposed this mod ought to also improve stability under braking, you’d be correct; and b) you may have recognized that this mod is a quick and easy way in which you can quicken your resident rack towards best achieving its static ratio; dynamically. Also correct.

Finally, I should mention that if you happen to have replaced the front A-arm bushings on a more recent (i.e current century) Ferrari, Maserati, or more particularly a Lamborghini, or Audi R8, you will have been confronted by a bushing that looks remarkably similar to ours, save for that it comes with an additional but mere steel front piece on its outer end, that appears to do something similar to Arm-Stops, although again for our purposes here, if perhaps IMHO only; less well (as amongst other things, besides being too expensive, they (unlike ours when Arm-Stop equipped) apparently still require too frequent replacement!).

**Lago Blue** · 24 February 2021, 12:28

The mechanics of the direct link between weakened A-arm bushings and steering response.

Suspension of Disbelief Part 1.e.

This will attempt to show how the typical wear that accumulates in A-arm bushes drives inaccuracy into our steering systems, and hint at how to remove and preclude same. The understanding of which may convince you to try this preventative mod.

I've borrowed a series of photos from Real Customs lovely Urq rebuild thread to help illustrate some points below. Looking at his car deconstructed, you can perhaps better understand my explanations and more easily visualize how the various parts move and act with one another; while the car is underway.

The forces great and small that act to cause these bush failures include both those of everyday braking and acceleration, and the occasional pot-hole. As I've described elsewhere, these can briefly amount to as much as thousands of Newtons against the joints of the suspension. It may be important to remember that our cars are both propelled forward and restrained from same, largely by a very few small rubber bushings each not much bigger than about half your thumb; and that they are only 'glued' in place inside their metal shells.

1st Photo: This less than 180 degree angle between the two tie-rods is a purposeful and necessary part of the Ackermann design here. But because the tie-rods attach to the strut brackets at an angle other than perpendicular to the long axis of the car, any fore/aft A-arm motion effectively shortens/lengthens the rods more quickly than if they did lay at 90 degrees.

2nd Photo: Installed, one can appreciate the small but unhelpful change in effective length that would immediately occur due to any resulting arc-swing through which these two rods must travel.

3rd Photo: The lines drawn attempt to show that any fore/aft A-arm travel must cause the tie-rod to swing, changing its' effective length, and in turn turning the wheel; off-course.

4th Photo: Starting at the tire's (imagined) contact patch, every accel. and de-accel. force will in turn drive the A-arm fore or aft, weakening the bushes; and set the above explanation in motion. Eventually, the bushings are so soft, any intended steering input always moves the A-arms first; before any change in wheel direction takes place. That this is happening constantly, often randomly and independently on each side of the car, is perhaps the most common source of vagueness in our cars steering. Ergo the Arm-Stops mod.

Audi steering rack and tie-rods attached showing rod dihedral Screen Shot 2021-02-11 at 20.41.12 copy.png Audi Steering tie rods, installed, viewed from above Screen Shot 2021-02-11 at 20.31.36.png Audi tie-rods w: eng. removed showing rod dihedral Screen Shot 2021-02-11 at 20.44.06 copy.png Audi - how bush weakness drives steering instability Screen Shot 2021-02-11 at 20.53.14 copy.png

Announcement

Wanted: Peer Review of Suspension Product

Wanted: Peer Review of Suspension Product

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