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: ZB 22 Hornet, 218 BeeSavage Mark IINotes: Standard 1 piece base for 2 piece system.Mounting Hardware Included