O.E.M. spacers typically wear out within a year of hard riding. O.E.M. wheel spacers should be checked and replaced as needed with every bearing service. Water and dirt act as a grinding compound between the seal face and the mating surface of the spacer. Once the grooves are deep enough, the sealing surface is lost, allowing water and dirt to pass through and contaminate the bearing. Designed for years of service even in the dirtiest riding environments. All Balls aluminum spacers feature a hardened steel shell pressed over the aluminum to provide superior wear surface. Manufactured with 52100 bearing steel that is through hardened, precision ground and zinc-plated for years of service. All kits contain wheel spacer(s) for one front wheel. Note: Kit contents will vary by fitment and are subject to change.