The Vism AR-15 flip up front back up sight is a low profile spring loaded A2 front sight post that mounts onto Picatinny Mil-STD 1913 rails. The AR-15 back-up iron sight flips-up and deploys with a push of a button and it is fully adjustable for elevation. Front sight height is designed for handguard rails, monolithic receivers, and gas blocks that are at the SAME height as the AR receiver Picatinny rail. Dimensions: 2.4"L X 1.1"W X 0.8"H. Sight has aircraft grade aluminum main body with steel A2 front post. Limited Lifetime Warranty.