The tritium Green Dot Sight System for Thunder 9 & 40 Fixed Set Sight offers the best low light performance of any night sights. Day and night, the shooter's aiming reference is three self-illuminated dots, identical in appearance and location under all light conditions. Get the Meprolight advantage with the brightest night sights available today. Meprolight sights are used and trusted by military personnel and law enforcement officials. All Meprolight Tru-Dot sights are covered by a 12 years usable illumination warranty to original purchaser.