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 compliance, use only the springs recommended by Edelbrock for each camshaft application.