Each Weaver base is machined to the tightest tolerances for a custom fit. They are designed to fight the effects of recoil with a square-cut notch that precisely mates to the sturdy cross bolt in every Weaver detachable ring. Fits: Smith & Wesson Models 29, 629, 625, L, K & N Frame Revolvers (Factory Drilled)Taurus L, K & N Frame Revolvers (Like S&W, Factory Drilled) Notes: This is a 1-piece base.Mounting Hardware Included.