WHITE RINGS: Bright & Tough Night Sights feature a white ring around the glowing dots for daylight visibility TRITIUM-PHOSPHOR LAMP: Tritium-filled glass lamp provides superior illumination in no light or low light settings SAPPHIRE WINDOW: Each tritium lamp is capped with a sapphire jewel which helps to evenly distribute the light from the tritium lamp as well as protect it from solvents and puncture PROTECTIVE ALUMINUM CYLINDERS: Contains and protects the tritium gas filled lamps from heavy recoil and harsh cleaning solvents Fits H&K Models. 45C Tactical, P30, P30L, P30SK, and VP9.