Diamondheads Polymer Diamond Rear Sight is designed for all AR15s and Modern Sporting Rifles. It is suitable for firearms fitted with a factory hand-guard and a fixed front sight, or can be paired with any Picatinny rail mounted Diamondhead Front Sight e.g. Diamond Front Polymer Sight, Diamond Front Combat Sight, Auto-Ranger Front Combat Sight, etc.Features: : Advanced Polymer/Composite construction for strength, light weight & exceptional durability: NiteBrite Photoluminescent Inserts the low cost alternative to Tritium can be charged by natural light or with a flashlight: Spring loaded sight flips up quickly with the push of a button, stays up securely and folds down flat: Patented Diamond shaped Apertures and Upper Housing for fast alignment with any Diamondhead Front Sight: Dual same plane long and short range apertures at exact same height as factory A2 sights: Defaults to either small or large aperture: Secure and accurate 0.5MOA windage adjustment