The BCM MK2 Receiver Extension is a precision-machined buffer tube designed for AR-15 M16 and M4 platforms. Manufactured from 7075-T6 aluminum to exacting Mil-Spec dimensions for reliable performance and durability.BCM MK2 Receiver Extension Buffer TubeMachined from 7075-T6 aluminum construction8-position adjustable designMil-Spec dimensions and specificationsCan reduce felt recoil when properly configuredRequires proprietary BCM MK2 buffer and rifle action springImportant Note: This buffer tube requires a specific BCM MK2 buffer weight and rifle action spring - standard carbine and rifle buffers will not work. Perfect for shooters building or upgrading their AR platform with BCM's enhanced recoil management system.