BMW=76g

IE HD = 76g

IE HD (top)
BMW (bottom)

IE HD (top)
BMW (bottom)

BMW

IE HD 

The anatomy of an M20 rocker arm:
Cast aluminum body, heat-treated

Tool steel or hardened carbon steel wear surface added as a casting insert

Press-fit bronze bushing for rocker shaft wear surface. 

The heavy duty rocker arms made by Ireland Engineering are a simple yet elegant solution to the factory M20 rocker arms which can fail due to improper valve adjustment (high impact loads) and high rpm. The BMW rockers do not last very long when run over 7000 rpm and are known to fail randomly at any rpm when the engine lacks proper valve adjustments in its service history. IE HD rockers are known to run 8000rpm+ on track reliably.

This is an easily reverse-engineered part and the main difference of the IE HD rocker over the BMW rocker is the thicker cross-section at the valve eccentric fork, which is the point of failure. There is also some stress-relieving on the underside via polishing. The rockers do not appear to be peened. 

Thanks to IE for making these upgrade parts for the M20!

If you do not want to shell out the cash for HD rockers, do not plan on revving past 7000, and want to reduce the chance of rocker arm failure, you can get BMW rockers shot peened, you can grind off the parting lines, and polish them .