Smith & Wesson K frame thumb piece nut, blue $10.00 Part 21 on the exploded diagram. Used, excellent condition blue thumb piece nut from a 19-4, K frame revolver. Will fit other models of K frame revolvers. Only 1 left in stock Smith & Wesson K frame thumb piece nut, blue quantity Add to cart Category: Smith & Wesson Related products Smith & Wesson J Frame Shooters Pack $39.97 Smith & Wesson K / L / N Frame Standard Shooters Pack $29.97