COMP Cams Hustler Valve Springs are an improved version of the popular GM LS6 "blue" valve spring. They are based on popular GM part #12499224 and #12565313 LS6 springs but with 4% higher seat and open loads for better dynamic control, as well as an extra .020" of lift capability. They are an excellent performance upgrade in GM 603/604 and CT525 LS crate Race Applications with tight rules packages.