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: H & R Models 155, SB2 Ultra Topper 158C for Post 1973 & all calibers of the Whitetail Classic, Lever action PardnerNew England Firearms Models Handy Rifle &/ Hornet, Huntsman Muzzleloader Notes: This is a 1-piece baseMounting Hardware Included