Made of highest quality spring wire and precision wound to close tolerances, our sure seat valve spring sets are for use on original equipment heads when installing Edelbrock Performer-Plus, Performer RPM and Torker-Plus camshafts. These are the same high-performance springs used on Edelbrock Performer and RPM cylinder heads. The #5900 series valve springs are designed for use with OEM valve rotators. Valve spring kits are complete kits that contain non-rotator valve springs, valve spring retainers and matching valve stem locks. For camshaft warranty compliance, use only the springs recommended by Edelbrock for each camshaft application.