Extensive R&D on all applications to provide high-performance components that last longer than OEM. Super-clean silicon wire used in valve springs is ground, not shaved, and X-rayed at regular intervals to check for flaws. Keepers not included; use OEM keepers and bases, as noted. Valves and guides are sold each; spring kits come complete for one motor and include instructions. All components made in the U.S.A..
