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 K frame mainspring $15.00 Smith & Wesson K frame Extractor rod collar $10.00