All Andrews cam kits for early Twin Cam 88 models require a heat-treated 34-tooth rear cam drive sprocket and 17-tooth steel crank sprocket The new sprocket replaces OEM sprockets Sprockets are made from heat treated alloy steel and are longer-than-stock for greater stability A full-length 3/16" drive key and 3 spacer shims are included With the shims, the installed length of new sprocket can be set to the same length as the original stock sprocket plus spacer 34-tooth and drive sprocket will fit all stock Twin Cam 88 model rear cam shafts If you are into any performance riding, a new sprocket is a must installation, even with engines using stock camshafts For chain drive cams only