Smith & Wesson K frame strain screw, blue $15.00 Part 55 on the exploded diagram. Used, excellent condition blue strain screw from a 19-4, K frame revolver. Will fit other models of K frame revolvers. Out of stock Category: Smith & Wesson Related products Smith & Wesson M&P .45 Guide Rod & Recoil Spring 16lb. $54.97 Smith & Wesson K frame Yoke, old style with gas ring $100.00