Fits 2004-2008 GM LS2/LS3/LS6/LS7 and 1997-2003 LS Engines when using Mr. Gasket Water Necks 2670, 2671, and 2672.;Opens sooner than stock at 160 degrees; High flow design for performance applications; Includes rubber o-ring seal/gasket; Incorporates pressure relief valve;