Nobody makes bases to fit as many guns as Weaver. Yet each base is machined to tight tolerances for a custom fit. They"re 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. Custom-hardened fastening screws come with every Weaver base.Used as Front base on:- Modern Muzzle Loading- Knight: MK-85, BK-92 (flat receiver)- SAKO: Whitetail HunterUsed as Rear base on:- Modern Muzzle Loading- Knight MK-95, BK-92 (flat receiver)- SAKO: Whitetail Hunter- Savage: 110-116 L/A, 210 shotgun(use X-High rings), 10-16 S/A(all pre "03 models)