This is a Yankee Hill Machine Co Sight known as the Flip Front Sight Tower, model YHM-9394.
AR-15 Front Flip Sight Tower- These front sights feature either a round hooded front sight guard that allows for fast and accurate sighting or a standard style front sight guard. They sight base features all steel construction for superior strength in demanding conditions. The flip sight is easily concealed with the push of a button. It flips up and locks in the deployed position. This sight accepts all standard AR sight posts and hardware (Included). With this setup you get the convenience of a flip front sight with the same weight as a standard AR sight tower. This sight's two-piece design allows it to be mounted on firearms with pinned and welded muzzle accessories
Features:
Mounts easily and securely with four cap screws using a 7/64 Allen wrench;Bore Diameter of 0.750 inches
