The Chevrolet Performance Aluminum Roller Rocker Arms have Chevrolet Bow Tie logos engraved into the main body which has exclusive multiplication feature, is CNC machined from extruded aluminum alloy with a pushrod seat made of 8620 steel. The bearings and fulcrum assemblies are lubricated with pressurized oil and have an extra-wide design for load distribution. Roller tip axle is made from 4130 steel and the roller tip is machined from 8620 steel. The rollers and valve stem tips have constant oil supply with reduced friction. The slotted main body is designed to provide extra rocker arm stud clearance while the needle bearing fulcrum reduces friction and adds horsepower over stock pivot ball style rockers. These aluminum rockers will not work with standard (short) height valve covers. Requires a tall-style valve cover for rocker arm clearance.