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 HK Front Folding BattleSight is easy to install and deploy, with no levers or springs to fumble with. Features: a Sight can be moved or taken off without permanent modification to the firearm a A stainless-steel cross-locking system ensures sights remain upright and zeroed under extreme combat conditions. a A push of a button folds the sights securely out of the way until you need them again a No tools required for adjustment