Utilizing the same proven PAC Racing ovate beehive springs as our High Pressure kit, our Steel Street spring kit features FEA-optimized and heat treated steel retainers. This kit was designed using the OEM spring seats. Kiggly Racing LLC offers this set as a cost effect, drop-in replacement the 4G63 applications looking to spin up to 10,000rpm and run up to 40psi boost. Seat pressure is 85lbs at 1.475". 325lb/in Rate. EVO 1-9 and DSM.