XS second-generation R3D night sights are engineered to give you a brighter, stronger set of sights. Easily install your sights with a set that requires 50% less force for installation. R3D sights are built to withstand years of EDC use and abuse. The set drives focus downrange using a serrated blacked-out rear sight and a dual-illuminated tritium photoluminescent front sight. R3D sights are the brightest notch and post option for fast and accurate shooting in bright and low light. Fits 17,19,22-24,26,27,31-36,38