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.Use as Front base on: - Beretta: Pintail ES 100 Slug Gun- Remington: 700, 78 L/A, 725, 40 X-L long actions, 700, 78 S/A, 722, 40X-S, 725 short actions, 700 ML- Ruger: M77(round top)- Sauer: 200- Weatherby: Mark V mag. except for 240 mag. Vanguard*Use as Rear base on: - Beretta: Pintail ES 100 Slug Gun- Colt: Sauer- Sauer: 200*Shimming may be required for proper scope alignment