Night Fusion's Perfect Dot night sights for Springfield XD pistols come in two models: One model fits XD A(R), XD(M) A(R), and XD A(R) Mod 2(TM) pistols. The other fits the XD-S(TM), XD-E(TM), 9mm Hellcat(TM) (Excludes 9mm Hellcat OSP(TM)). Like all night sights, Perfect Dots use self-illuminating Tritium to get the "always on" glow with a difference: PDs have 30% more Tritium, so they are brighter than other night sights. The Tritium insert isn't surrounded by a painted-on ring, but rather one made of a daylight fluorescing material that produces optimum visibility in daylight. The result is what the Night Fision folks have dubbed the "Per Mfg: Night Fision