The ML10222 family of sights is meant to fit the 10mm and .45 ACP pistols. These are the G20 ,21,19, 30 and 36 pistols . This set is not for the G37 in .45 GAP Caliber. This is a fixed set. Meprolight sights 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.