Smith & Wesson N frame strain screw, blue $15.00 Part 55 on the exploded diagram. Used, excellent condition blue strain screw from a Model 57, N frame revolver. Will fit other models of N frame revolvers. Out of stock Category: Smith & Wesson Related products Smith & Wesson M&P .45 Guide Rod & Recoil Spring 16lb. $54.97 Smith & Wesson M&P 9mm .40/.357 Recoil Spring 16lb. $14.97