JEGS Rocker Arm Shim Kit will correct the lifter preload on engines with non-adjustable pedestal mounted rocker arms. If you swap camshafts, mill the cylinder heads, change valve springs or make other changes to your engine, our shim kit provides the preload and saves you from having to order custom length pushrods. Each kit contains 16 pieces of 0.030" and 16 pieces of 0.060" shims which can be used individually or combined to make a 0.090" shim.