034Motorsport Street Density Snub Mount - B7 RS4 / C5 RS6034Motorsport Street Density Snub Mount B7 RS4 C5 RS6 Density Line Mounts are manufactured from high durometer rubber instead of polyurethane for a number of reasons. While vulcanized rubber mounts are more expensive to prototype due to increased complexity of manufacturing and high initial tooling costs, rubber is inherently better than polyurethane as a damping medium for mounts. Rubber is able to deal with stress under both tension and compression,