CNC machined aluminium with steel fittings. Black anodised finish. Locking ring on one end and grub screw on the other. Overall length ~ 62mm. Weighs approx 134 grams. Converts AR-15, M4, M16, SR25 series rifles fixed butt stocks to folding. It takes a lot of force to push against the spring, to unlock from the inline and folded positions. Do not fire the rifle when in the folded position, this adapter is purely to aid storage of the rifle. Connection thread code ~ 1-3/16 inch UN16. Compatible with most 4 and 6 position retractable stocks.