These bushing kits were created to be a replacement or upgrade for your GrimmSpeed Pitch Stop Mount. The red bushings are the same durometer rating as our standard pitch stop; 80A. The black kit is the same set of bushings that comes in our Race Version Mount in a stiffer 95A durometer rating. If the bushings in your current GrimmSpeed Pitch Stop Mount are starting to see some wear and are in need of replacement, or you want to upgrade to a stiffer bushing (or vice-versa) these are exactly what you need!