The Warne Maxima Vertical PA Scope fit Weaver style cross slot bases and incorporates a Warne square stainless steel recoil control key in both the front and rear rings for positive engagement of ring to base. This ensures a “no slip” positive recoil surface across the slot of the base and to withstand the heavy recoil. The Maxima square recoil key also protects against swaging or peening of the bases when used on softer or less durable materials. The Maxima Fixed ring band is wider for additional clamping surface around the scope to hold the optic firmly in place