Crower's Enduro aluminum stud mount roller rocker arms are fully CNC machined from USA made, premium aluminum extrusion. Crowers unique "full arch" design reduces the rocker flex found in other brands. Results are increased rpm, greater area under the lift curve and added spring clearance (1.625"). Double-step, serrated pins feature our rotor clip design that eliinates pin loosening. USA made needle bearings.