Strut Bump Stop 1K0412303F: 55mm Polyurethane Front Suspension Buffer for VW Golf, Jetta, Eos, CC and Audi A3

Bonpora number 4110021 is a polyurethane strut bump stop manufactured to match OE 1K0412303F, the 55 mm front suspension buffer used across a wide range of Volkswagen Group platforms from the mid 2000s onward. This guide is written for importers, parts wholesalers and workshop buyers who search by OE number, by vehicle model or by supplier, and it collects the fitment data, PR code logic, cross-reference numbers and sourcing terms for this part in one place.

What Is the 1K0412303F Strut Bump Stop?

In the official Volkswagen catalog the part appears under the name rubber stop for shock absorber, 55 mm. It is a progressive foam buffer that sits on the piston rod of each front strut, inside the dust boot. When the suspension reaches full compression, for example over a deep pothole or while carrying a heavy load, the buffer cushions the last part of the travel and protects the strut, the chassis and the occupants from a harsh metal-to-metal impact. Because the material compresses progressively, the buffer also works as a secondary spring and keeps the front axle controlled during brief overloads.

Volkswagen lists the part as serviced with the strut assembly. In practice this means that when a workshop replaces worn front struts, the bump stop and the dust boot should be renewed at the same time, since both parts age with mileage, heat and ozone exposure. A buffer that has turned brittle or split no longer protects the strut and should be replaced even when the strut itself is still serviceable.

1K0412303F Vehicle Applications

Catalogs tie this buffer to front suspension builds on the VW A5, PQ35 and MQB platforms and their Audi, Seat and Skoda derivatives. The table below summarizes the main published applications. Production region matters here: some Golf and Beetle applications were built in Mexico, and generic European catalogs sometimes omit those entries.

In most configurations the per-car quantity is two, one buffer per front strut. A small number of catalog configurations list a single piece, so confirm the quantity against the vehicle VIN or PR code before ordering in bulk.

PR Codes Decide the Exact Version

VW does not assign this buffer by engine alone. The parts system selects the 55 mm F revision only for front suspension builds carrying specific PR codes, for example G02, G06, G07 and G08 shock absorption in front, the 2UC sports version, 2UA standard design and 2UD comfort design, combined with front wheel drive 1X0 or four wheel drive 1X1. North American catalogs describe the 2012 Golf application under suspension code G09 for the 2.0 liter engine without electronic damping and the 2.5 liter engine. For wholesale buyers this means the same Golf model line can require different bump stop heights depending on the factory suspension package, and the most reliable confirmation comes from the VIN rather than the model name.

Beetle and Mexico-Built Golf Applications

The 2012 to 2016 Beetle and Beetle Convertible, together with Mexico-built Golf models from 2014 to 2016, are frequent blind spots in aftermarket listings. Catalog data ties these cars to PR combinations such as 2UC with G22, G17, G51 and G54. Distributors serving North American and Latin American markets should verify these applications explicitly, because demand for the buffer in those regions is steady while listing competition is thinner than for the mainstream Golf and Jetta applications.

Technical Specifications of Bonpora 4110021

The VW catalog dimension for this buffer is 55 mm in height, while the measured Bonpora sample stands 56 mm. A difference of about one millimeter is normal for foam buffers, because suppliers measure with or without the molded top cap and the material settles slightly with handling. Both values describe the same F revision build.

Height and the Suffix Letter: Inside the 1K0412303 Family

The 1K0412303 base number covers a long series of revision letters, from early builds up to later letters such as G. Each letter is a distinct build with its own height and density, matched to specific suspension setups, so the suffix is not cosmetic. The F revision is the 55 mm front build, and several aftermarket brands list the F and the earlier E revision as comparable references for many applications. Dealer parts systems often propose a later letter than the one originally fitted, which is normal supersession practice; for a warehouse buyer the decisive physical check remains the uncompressed height together with the outer and bore diameters.

How to Measure Your Old Bump Stop

Remove the buffer from the strut, let the material recover for a few hours, then record three values: uncompressed height, outer diameter and bore diameter. Bore shape can be stepped, and catalog data for this family lists inner diameters of about 30 and 23 mm at the two ends, so measure both openings. Compare the three values with the specification table above and select the revision whose height matches. Guessing by model name alone is the most common cause of returns in this category.

Cross-Reference Numbers for 1K0412303F

European and North American aftermarket brands distribute this buffer under their own numbers. The following references map to the same 55 mm front application and are useful when a customer requests a specific brand or when quotations need to be compared line by line.

Polyurethane Advantages for Strut Buffers

Original buffers are molded from open-cell foam that hardens and crumbles with age, ozone exposure and repeated compression. Bonpora produces the 4110021 buffer in polyurethane with a consistent cell structure, which keeps the compression curve progressive over a longer service life and resists the temperature range around the strut tower better than standard foam. For fleet and wholesale buyers the practical benefit is fewer warranty claims on the buffer itself and less secondary damage to the strut it protects. The full polyurethane bump stop program covers additional heights for the same platform family.

Replacement Symptoms and Service Recommendations

• Visible cracks, splits or missing chunks on the buffer body
• Flattened areas or permanent compression set after frequent bottoming
• A clunk or bang from the front axle over dips and sharp bumps
• Worn or torn dust boots, which expose the rod area to grit and moisture

Replace buffers in axle pairs even when only one side is damaged, because the two sides age together and unequal heights upset front axle behavior. When the struts come out, the matching shock absorber parts program covers boots, mounts and strut bearings, so the complete corner can be renewed in one visit. Buffer, boot, mount and strut renewal on both sides is the standard service pattern for these platforms, and it is also the pattern that end customers accept most easily when the labor is already booked.

Wholesale Sourcing from Bonpora

Bonpora manufactures suspension buffers and related components in China and exports under neutral export packaging with private label options. The factory supports OEM and custom design: buyers can send a drawing, a physical sample or the OE number and receive dimensional confirmation before the order is confirmed. Standard delivery time is 15 to 30 days depending on order size, and every shipment carries a 1 year warranty. For buyers building a mixed container around Volkswagen Group applications, the 4110021 buffer can be quoted together with chassis and suspension parts such as control arms, links and bushings from the same supply chain, which simplifies customs paperwork and warehouse receiving.

Request a quotation for Bonpora 4110021 / OE 1K0412303F. Send the target quantity and destination port, and the sales team will return packing details, gross weight and unit pricing for the 55 mm front buffer, together with lead time for your region.

Frequently Asked Questions

Is 1K0412303F the same part as 1K0412303G?

No. The letters mark different builds inside the same part family, with different heights and suspension assignments. The F revision is the 55 mm front buffer described in this guide, while other letters serve other suspension packages. Match the height and the diameters of the removed part before ordering, and treat dealer supersession suggestions as valid only when the physical dimensions agree.

How many buffers does one car need?

Most configurations use two, one on each front strut, and pairs should be replaced together. A small number of catalog configurations list a single piece, so confirm the quantity against the VIN or the PR code combination of the vehicle in question.

What happens if I keep driving with a failed bump stop?

The strut bottoms out on full compression, which sends harsh impacts into the chassis, accelerates wear on the strut rod seal and can lead to oil loss and early strut failure. A new buffer costs a small fraction of a strut assembly and should be renewed as soon as damage is visible.

Can Bonpora supply custom buffer sizes?

Yes. The factory offers OEM and custom design support, including mold development for non-standard heights, diameters and bore shapes. Buyers can submit drawings or physical samples, and the engineering team returns dimensional drawings for approval before production starts.