Reliability Enhancement Kit Features 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. Reliability Enhancement Kit Specifications Brand: Geissele Automatics Model: Reliability Enhancement Kit Caliber: 5.56mm Firearm Type: AR-15 Material: Steel