Smith & Wesson K frame mainspring $15.00 Part 88 on the exploded diagram. Used, excellent condition mainspring 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 9mm .40/.357 Recoil Spring 16lb. $14.97 LPA Smith & Wesson M&P Fibre Optic Adjustable Sight Set. $195.00