Compatible with Mil-Spec AR-15 stocks, the San Tan Tactical Standard Mil-Spec AR-15 Carbine Buffer Tube Kit contains all the necessary parts to mount a stock assembly onto your lower receiver. The six position AR-15 buffer tube is machined from 6061-T6 aluminum with a MIL-A-8625 Type II, Class 2 standard anodized finish. The design features a precise drainage hole that removes water from the system in marine environments. For optimal performance, their standard offering includes a carbine recoil buffer body and quick detach receiver end plate are made from 6061 aluminum, a spring made from high-tensile steel, and a castle nut is made from high-carbon steel. Features6061-T6 Grade Aluminum6 Position Mil-Spec Carbine Buffer TubeCarbine Recoil Buffer 3ozHigh-Quality Recoil SpringCastle Nut & QD Receiver End Plate