16 New Z28 style .550 Lift performance valve springs, hardened spring retainers and hardened valve locks. Bundle includes 16 springs, 16 hardened spring retainers, & 32 valve locks. These springs are stock outside diameter and can be used in many 1955-1993 small block chevy V-8 cast iron cylinder heads. They work great for stock, towing, and most mild performance cams and work best with cams up to .550 lift.