The Sylvan Arms Scorpion Adapter allows you to add an aftermarket pistol buffer tube accessory or arm brace, improving your weapon control. Product Details Threaded 1 3/16 x 16 to pair with all standard AR-15 buffer tubes/receiver extensions Fit: Scorpion EVO 3 S1 Material: 6061-T6 Aluminum Finish: Flat Black Anodized NOTE : Gunsmith Installation Recommended