Features: Pro Series Flip-Up Rear sight is a low profile spring loaded rear back-up sight that flips-up and deploys with a push of a button. Rear sight low profile design folds flat to fit under the majority of scopes. Features an A2 dual aperture (large & small) that is fully adjustable for windage. Knurled windage knob makes adjusting the windage an easy task. Dimensions: 2.4"L X 1.2"W X 0.8"H Weight: 2.3 oz. Aluminum main body with steel A2 dual rear aperture windage knob and adjustment screw. Mounts onto Picatinny Mil-STD 1913 rails mounting tool included. US. PAT. 9976834