Troy Industries' Tritium BattleSights(TM) are designed to eliminate the poor sight orientation that is typical in twilight. Tritium is a form of hydrogen that emits a continuous light source when batteries or electricity are not available. The front post is centered between two Tritium points of reference to allow proper alignment. Durability and dead-on accuracy make Troy BattleSights the hands-down first choice of Special Ops and Tactical Users Worldwide. Troy's M4 Front Folding BattleSight is easy to install and deploy"" with no levers or springs to fumble with. No tools required for adjustment.