The Apex Evolution IV Hammer for Smith & Wesson N-Frame revolver allows the user to tune the revolver for a lighter trigger pull weight by adjusting the strain screw for lighter main spring force, without sacrificing reliability. Semi drop-in replacement of factory hammer(minor fitting may be required) Reduction in trigger pull weight by adjusting strain screw. Converts revolver to Double Action Only(DAO), lacks a hammer spur for cocking. Works in current production S&W N-Frame centerfire revolvers only. Mfg: Apex Tactical Specialties Inc