PFR57-106 has been designed to replace the rear trailing arm front bush where the arm locates onto the chassis. These bushes are no longer available from Porsche unless you buy the complete arm at a cost of over 1000.00. The RS model had a stiffer bush fitted over the standard non RS models, the Powerflex bush will upgrade the standard bushes to a similar stiffness to that of the RS version. PFR57-106 comes with Oil Lite bearings to allow the arm to pivot freely allowing the suspension to work with no loading from the bush with positive location.