Fits Glock Models: 20 21 29 30 36 40 and 41 (including S and SF variants)Designed for shooters who want daylight brightness and a constant aiming point the dual illuminated Trijicon DI Night Sights are equipped with an industry-first interchangeable fiber. This patent pending design not only allows the ability to replace the fiber in the field it allows the user to choose among several fiber and ring retainer colors to configure a personalized aiming solution.Trijicon DI Night Sights feature a chemical and heat resistant fiber finished with the same proprietary technique as the Trijicon ACOG coupled with a tritium lamp capped with a sapphire jewel. This dual-illumination technology amplifies collected light ensuring an ultra-bright aiming point in any light from daylight-bright to low-light to complete darkness.