SuperPro DURO4428K SuperPro DuroBall Additional Caster Offset Front LCA Inner Rear Bushing Kit - Subaru VA WRX & STISuperPro DURO4428K SuperPro DuroBall Additional Caster Offset Front LCA Inner Rear Bushing Kit Subaru VA WRX & STI Control arm bushings form the vital pivot and link between all core suspension components. SuperPro increases the performance and precision over traditional elastomer bushings with the compound DuroBall bushing assembly. Using an isolated spherical bearing encased in polyurethane provides the precision and articulation of a bearing design