Leapers UTG Model 4/15 Comm-Spec 6-Pos Extension Buffer Tube - Black - TLU006. 6-position Receiver Extension Tube with Commercial-spec Diameter for Modern Sporting Rifles. Precision Machined from 6061/T6 Aircraft Grade Aluminum. Matte Black Anodizing with Mil-spec, Type III Hardcoat, Class II. Tightest Tolerance Control for Zero-gap Fit with Polymer Stock and Receiver to Meet Most Demanding Silent Operations. 100% Proudly Made in USA for Most Serious Users.