These locking header bolts fit the GM LSx V8 (LS1, LS2, LS3, LS6, LS7). They measure 8mm-1.25 x 22mm and come with 12 in a package. Stage 8 Locking Header Bolts easy to use but they are absolute insurance against horsepower loss or gasket failure created by loose nuts or bolts. The unique patented and trademarked functional design is just three pieces: a bolt (4130 Alloy Steel), a locking retainer and a spring clip or, depending on the application, a nut, a locking retainer and a spring clip. The bolts are application specific as either hex head with a 3/16 recessed allen head or 12 point, both come in multiple lengths. All Stage 8 Locking Header Bolt Kits are sold as kits with all of the necessary hardware for your application.