Gas block height flip up front sight features elevation adjustable front sight post. Designed to be mounted on top of picatinny gas blocks lower than the AR-15 receiver rail. Aluminum and steel construction to withstand high heat from prolonged firing sessions. Sight may be used as a flip-up front sight, back-up iron sight, or used with an optic. This flip up sight takes up 2.1" of rail space when folded and 1.2" when deployed.