These Hogue grips are a two piece that replaces the one piece stock grip. These grips are a curved backstrap design that installs using a mainspring retainer and screws which come with the grip. The mainspring retainer is pinned into position with the pin that holds the stock grip on. The mainspring retainer provides the threaded bosses that the grip panels screw into. Notes:Fits models: 4506,1006,1066,1046,1086,4546,4566,4586, CQB .45, etc.These are full size single stack magazine .45 and 10mm caliber semi auto pistols.Will not fit frame decocker models with a "2" or "7" in third digit such as 5676, 4026 etc