Meprolight's combat proven self-illuminated night sights enable you to hit stationary or moving targets under low-light conditions with dramatically increased hit probability. Designed as replacement parts for the standard weapon sights the Self-Illuminated night sights can be mounted directly with minor modifications.The Meprolight Tru-Dot model offers a handgun sighting system for improved rapid instinctive aiming which requires no transition from day to night use. Day and night the shooters aiming reference is three solid dots identical in appearance and location under all light conditions.This front sight model is compatible with Ruger SP101.