Not all Nickel Boron is created equal and FailZero is the undisputed pioneer of Nickel Boron technology. When failure is not an option, you can depend on FailZero. The M16 Bolt Carrier Group is fully assembled and drop-in ready for most MIL-SPEC upper receivers. All critical parts are coated with EXO Nickel Boron technology providing permanent dry lubricity, extreme durability and increased wear and corrosion resistance. This patented Nickel Boron coating will reduce friction and improve the overall performance of your rifle.