This is a TROY Sight known as the BattleSight, model SSIG-IAR-SMBT-00.
Troy BattleSights(TM) set the world standard for performance and durability. Now" Troy has developed a rugged low-profile sight designed for firearms with top rails higher than the standard M4. For shooters who favor a sightline that's as close to the barrel as possible" or for those with raised top rail systems" the Troy Micro BattleSight provides an ideal solution.
Features:
Troy Micro BattleSights are rugged reliable and BattleReady