Speedmasterª DNA_ roller rockers are the toughest and most innovative rockers we've ever made. Crafted from certified aircraft-quality, heat-treated aluminum, they're matched to massive, precision-ground trunnions for superior durability, and optimized rocker arm geometry evenly distributes the load for maximum strength. DNA_ rocker arms also utilize oversized needle roller bearings for better load distribution and longer service life. Finally, they're black anodized; you'll want to leave your valve covers off! Speedmasterª Aluminum Shaft-Mount Rockers can withstand valve spring loads up to 700Ibs, the extruded body has a tensile strength of over 60,000 PSI.