The springs conical design features a smaller diameter in the upper half to reduce active mass. This reduction in mass, along with the progressive frequency created by the conical shape, dampens coil oscillations better than any other spring design. These improvements allow for the use of more aggressive Camshafts and an increase in RPM limit speed. Finally, Superfinish processing of the springs results in increased durability and spring life.Kit includes:#7230-16 Conical Valve Springs#1774-16 +.100 Tool Steel Retainers#623-16 Valve Locks#511-16 Valve Seals#4680-16 Spring Seats