They come in one size...there is a SHIM under the rocker arm that comes in diff thickness. Those U need to measure to find out which ones U need...using a feeler gauge :) U only need to do a measurement if U loose the shims under the rocker arm- they sit on top of each valve/spring. Mike Jez. > Big Question-- > Is a rocker arm a rocker arm or do they come in different grades like > bearings?