WMD Bolt Carrier Groups are coated in WMD's proprietary NIB-X coating (40% more wear-resistant than chrome) and polished to a presentation-grade sheen. This top-quality Bolt Carrier Group resists fouling, needs little lubrication and can be cleaned easily with a wipe of a cloth. WMD's testing has run thousands of rounds between cleanings without malfunctions. Military personnel have praised its performance in desert conditions where heavy lube can collect dust and dirt. The WMD NIB-X BCG is extraordinary reliable, helps the gun run cooler and dramatically reduces the time you'll spend cleaning your gun. The Bolt is made of Carpenter 158 steel, is heat-treated, shot peened, magnetic particle inspected and has Milspec gas rings installed. Black extractor buffer and heavy-duty spring installed. NiB-X coated for durability and ease of cleaning. The Bolt Carrier is an M16 Full Auto style (heavy weight) made of 8620 material, heat treated, case hardened and NiB-X coated. The Gas Key is hardened to USGI specs, NiB-X coated and attached using grade 8 hardened fasteners. Properly staked per military specifications. Includes NIB-X coated hammer.