The Yankee Hill Gas Block Mounted Front Flip Sight is a durable, all steel sight that attaches to any railed gas blocks to give you a backup iron sight. This sight folds out of the sight line with ease. A push of a button and it flips and locks in the deployed position. How easy is that?! The Gas Block Mounted Front Flip Sight mounts quickly and easily with the included thumb screw. It accepts all standard AR sight posts and hardware (included).