This listing is for 16 brand new set of Z28 style .550" Lift performance valve springs, hardened spring retainers and hardened valve locks. Set includes 16 springs, 16 hardened spring retainers and 32 hardened valve locks.These springs are stock outside diameter and can be used in many 1955-1993 small block Chevy V8 cast iron cylinder heads. They work great for stock, towing and most mild performance cams and work best with cams up to 0.550" lift.