The bump stop is a stiff foam block that slides over the shaft of your front strut or rear shock. Under full compression the bump stop prevents the shock from completely bottoming-out, causing damage to the shock or to the chassis. In other scenarios the bump stop can actually play an active role in the handling and stiffness of the car. Because of their placement, bump stops are subjected to debris, moisture, and heat and this can degrade its performance or cause it to fail compeltely. BMW insists on new bump stops any time a new shock is installed on a car*.
* - many aftermarket performance shocks like Bilstein or KONI will come with their own bump stops and new ones are not required. This does not apply to any Bilstein or KONI or other brand marked as "OEM".
This is a bump stop manufactured by Rein (CRP) Automotive - an original supplier to BMW for many mounts and bushings. As an OEM it meets all of BMW's original design, fitment, and performance requirements and is TUV approved. OEM parts are the best alternative to more expensive Original BMW parts because they are virtually identical without the inflated price tag. This part has a two year warranty.
BMW Fitments:
3 Series
E46 (99-05) > 323Ci
E46 (99-05) > 323i
E46 (99-05) > 325Ci
E46 (99-05) > 325i
E46 (99-05) > 325xi
E46 (99-05) > 328Ci
E46 (99-05) > 328i
E46 (99-05) > 330Ci
E46 (99-05) > 330i
E46 (99-05) > 330xi