This is a Midwest Industries Sight known as the Combat Rifle Sight, model MI-CRS-R.
Midwest Industries' combat rifle rear flip slip is designed to have a super low profile. When folded down it has a .388" centerline and flips up to full Mil-Spec height. The intermediate aperture is perfect for long-range precision and close-range rapid engagement. Dual locking detent springs are added for reliability and crisp positioning. The combat rifle rear flip sight is constructed of phosphate finished ordnance grade steel and 6061 aluminum hard coat materials. This rear sight also has rifle .5 MOA and carbine .65 MOA click adjustments.
Features:
For AR15/M4/M16 Rifles and other platforms
Super low profile .388 centerline when folded down;Flips up to Mil-Spec height;Intermediate aperture;Rifle .5 MOA / Carbine .65 MOA click adjustments