The ML10224 family of sights is meant for use on the 9mm,.357 Sig,.40 S&W and .45 GAP caliber pistols. These would be the G17,19,22,23,31,32,33,34,35,37,38 and 39 Gap Caliber. This is a fixed set with Orange rear/Green front. MEPROLIGHT sights, like our other self-illuminated products & devices take maximum advantage of tritium light sources - the fail-safe, maintenance-free light sources that don’t require any external source of energy and provides up to 15 years of usable light under all weather conditions. MEPROLIGHT continues to offer the strongest guarantee in the industry for the usable light of our TRU-DOT sights