Trijicon SA-22 Sigma .40 3 Dot Front & Rear Night Sight Sets are designed and assembled with the optimum combination of strength and safety. The patented aluminum cylinder and sapphire lens construction cannot be equaled. The brightness obtained from the tritium content is focused through the sapphire lens to give the maximum possible illumination. Because the sight blades are machined from steel rather than cast, their strength is unsurpassed. Trijicon night sights are the brightest, strongest and safest.