The Ruger Bright & Tough Night Sight Set (Yellow) from Trijicon is a three-dot iron sight designed to improve your accuracy with your SR9/9C, SR40/40C, or SR45 revolver in bright light, low light, and no light. Two glowing yellow dots in the rear sight help align the green front sight with your target. A green tritium phosphor lamp is used in the front sight since green provides more contrast against muzzle flash than other colored phosphorescent gas. The green lamp is also easier for the human eye to visibly acquire in any lighting condition. This configuration of the Bright & Tough Night Sight is intended for a Ruger SP101 revolver, and is engineered to withstand the force of rapid firing and shock. Trijicon recommends that you seek professional installation to avoid damage to your sidearm.