Stage 8 Locking Header Bolts easy to use and they are REAL ASSURANCE 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. The header bolt kits are application specific as either hex head with a 3/16 recessed allen head or 12 point, USA or metric. All Stage 8 Locking Header Bolt Kits are sold with all of the necessary hardware for your application.