This buffer tube is has 6 positions for a collapsible stock to engage for length adjustments. It has the standard drain hole in the back end and mil-spec thread dimensions and tube diameter. Designed to thread into any AR-15 receiver or AR-15 stock adapter that uses mil-spec threads and can be used with any mil-spec AR-15/M4 collapsible butt stock. Precision machined from 6061/T6 Aircraft Grade Aluminum to tight tolerances for a precise fit with receiver and stock. Precision rolled threads and matte black anodizing with Mil-Spec Type III, Class II Hardcoat finish. Made in the USA. This buffer tube is one of the best values on the market for a high quality buffer tube at a reasonable price.