The Sylvan Arms Folding Hinge Stock Adapter allows you to fold your stock and significantly reduce the length of your rifle for easy stow and travel. - Specifically designed for gas piston and direct impingement systems 5.56 to .308 systems as well as .223 compatible it has standard 1-3/16 x 16 thread and does not require any additional parts to be used with standard BC Groups. - It is CNC-machined in the USA from 7075 Billet Aluminum making it uniquely lightweight and corrosion resistant. This assembly weighs only 6.0 ounces. No special tools required; only a standard armorer's wrench. The product does not need to be disassembled in order to install it on to your rifle/pistol. - Simply screw on fold and carry! - SPECIFICATIONS - Fit: platforms .223/5.56 to .308 & most 9mm: - 9mm bolt carriers with 5/8 ID (.625) standard sizing can use the bolt extension included after removing the pin and weight from the bolt carrier - Surface treatment: hard coat black anodized - Material: 7075 CNC-machined billet Aluminum - Thread specifications: 1-3/16 X 16 - Hinge dimensions: 3 11/16 inches - Hinge weight: 6.0 oz BC Extension 2.2 oz - Hinge length: 1.3 inches - Warranty: limited lifetime