These silicon vanadium constructed springs are stress relieved and fully polished for maximum longevity. 155lbs on the seat at 1.800" installed height and 405lbs @ 1.150" with coil bind at 1.100" and max lift is .650". This dual spring has a stock LS outside diameter of 1.295" to fit all the LS heads. Choose the 6.SPS515 spring seat for this spring and the 6.RET515 titanium retainer for SBC engines and the 6.RET520 titanium retainer for the LS engines. This spring is great for our ZZx and ZZ9x cams and also for our 242i and 264i solid rollers. For the LS cams, the ZL13, ZL15, and ZL17. Sold as a set of 16.