M-Eight High-Load springs are machined from a premium grade hi-tensile chrome silicon single conical ovate wire, shot-peened with a specially processed thermal heat treat and super NexTex. finish to give these valve springs the needed fatigue life to exceed the high demands of V-Twin engines from stock to performance. Valve springs are a direct bolt in replacement, no spring seat or rocker cover machining required up to .565in lift. Springs will accommodate over .600 cam lift, but will. require spring seat pocket machining on the cylinder heads to set correct spring open height. Smaller lighter weight retainers which drastically reduce the valve weight creating a quicker revving and smoother motion than comparable dual or single valve springs. Eliminate valve spring separation, maximize stability, reduce valve-train noise and harmonics. Packaged as a matched set and must be installed at the correct OPEN HEIGHt. Matching max cam lift to the open height spec of the valve springs is essential for optimal valve-train operation and spring life (see included spring spec chart). Kit includes: matched set of Feuling High-Load BeeHive valve springs, Titanium retainers, machined spring seats, seat shims, valve locks and a set of premium Viton valve seals equipped with a spring loaded valve stem wiper system. Bolt in up to 565 lift for M-Eight. Fit up to .600in lift. M-Eight specs: seat lbs. / installed height; 151 lbs. at 1.475in (.485in lift), 144 lbs. at 1.498in (.508in lift), 143 lbs. at 1.501in (.511in lift), 140 lbs. at 1.511in (.521in lift), 124 lbs. at 1.562in (.578in lift), 120 lbs. at 1.582in (.592in lift), 304 lbs at .990in open height, coil bind at .945in (cam specs. measured on the lifter at .050in lift with 1.61 rocker arm ratio). Recommended for .540in+ lift camshafts.