The Geissele Reliability Enhancement Kit includes the Geissele Reliability Enhanced Bolt Carrier Group and the Geissele Super 42 Braided Wire Buffer Spring & Buffer in your choice of H1, H2 or H3 configuration for 5.56mm AR-15 pattern rifles. The Geissele REK is the culmination of a many years of extensive testing and fine tuning to bring you the most reliable operating system upgrade you can make to your carbine. The Geissele Reliability Enhanced Bolt Carrier Group is a 5.56mm full-mass, full-auto rated M16/M4 bolt carrier group. The carrier features a properly torqued and staked, Chrome Lined, Nano coated, gas key. The cam pin is machined from an advanced tool steel also used to produce medical instrumentation known as H13, it is then coated with Nanoweapon (Chrome-Nitride) for maximum corrosion and wear resistance. The extended upper rails on the carrier also provide much greater stability and dramatically increase feeding reliability. The Carrier is coated with Nanoweapon for m...