The AR-STONER Deluxe Collapsible Stock Kit is perfect for upgrading an existing AR-15 to a carbine collapsible stock system, or building a new carbine rifle. This assembly is machined to exacting standards to provide excellent fit, reliable function, and performs in the harshest conditions. Rest assured the high-grade, impact extruded, 7075-T6 aluminum Extreme Duty Buffer Tube will perform in high stress situations when reliability is essential. With a hard coat anodizing, machined to strict military standards, and with an 84% increase in tensile strength over the 6061 aluminum standard duty buffer tube, this Extreme Duty Buffer Tube Assembly is able to withstand years of abuse. The buffer spring has also been upgraded to a stainless steel unit for corrosion resistance in harsh environments. Includes:B5 Systems Bravo Stock6 Position Buffer Tube (1.148" Diameter)Stainless Steel Buffer SpringRecoil Buffer (3.04 oz)Castle NutEnd Plate FeaturesErgonomic cheek weld.Color-matched steel ha...