These are M20 heavy duty cast rocker arms. Designed to be extra thick on the adjuster side to eliminate the fatigue failures which are common with factory rockers. They are polished and shot peened with very few casting marks. Use standard BMW adjuster hardware. These are a good idea for any engine rebuild; stock, performance, or race. These rockers are standard in all of our in-house engine and cylinder head builds! They are also SpecE30 Legal!