The extension tube is made of high-quality 6061-T6 aircraft grade aluminum and has precisely rolled threads for durable thread engagement with lower receivers. It has undergone the tightest tolerance controls for a secure fit and function with various collapsible stocks. The extension tube is finished in a matte black Type III Class II hard coat anodize, which provides a durable and corrosion-resistant finish. This product is proudly designed and made in the USA, ensuring its quality and reliability. Product Features 6-position Receiver Extension Tube with Mil-spec Diameter for AR15 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 Product Specifications Material: Aluminum Height: 1.45" Length : 7.25" Weight: 4.0 oz Color: Black Anodize