This is an upgrade for the stock 968 caster block. The rubber is replaced by Igus iglide plastic bushings with stainless center bushings. These are designed to reduce friction and allow the control arm to freely cycle while not allowing changes in caster/toe. These are designed for race-car use and probably not the best idea for street driven cars due to the increased NVH. They are designed to be 944SPEC compliant as the plastic and center bushing are identical in dimensions to the stock rubber bushings.