Ok heres my worth,when I rebuilt my 68 charger R/Ts suspension,I used PST lca poly graphite bushings.They had a "bulge or bumper" forward edge which,once in place helped control the forward movement of the arm. The ones they supplied me w/(at the time) used the inner and outer shells from the OE bushings.I dimantled 2 new rubber lca bushing and used the shells for the polys.Once the polys were in the outers, I pressed the inner sleeve into the bushing which locked it in place.Ive never had any problems w/the polys in ten years,But they are a love /hate kinda thing, guys either like them or they don't,D