These are Viton o-rings from Schmidty Racing Suspensions used on Walker Evans shocks to go between the steel shock mounting bushings and the shock eyelet bearings. Compared to the OEM rings and silicon, these o-rings are made from viton which has a higher durometer (tougher) rating as well as higher petroleum resistance. These do not become soft, swell out, and/or tear like the OEM ones do.