Smith & Wesson Mainspring Stirrup S&W 38-3, 49-3, 60-9, 317, 331, 332, 337, 337PD, 340, 340PD, 342, 342PD, 351PD, 360, 360PD, 431PD, 432PD, 442, 637-1, 638-2, 642 (for use with Mim Hammer Only)