Leupold�s famous rotary dovetail rings in BOTH front AND rear bases; there�s no way a ring can shoot off its base. Ideal for large caliber, heavy kicking rifles that can throw a scope off easily, plus light caliber varmint rifles that need an absolutely rigid scope mount to make full use of the gun�s accuracy potential. Dual Dovetail Bases and Rings must be used together; will not interchange with other Leupold rings and bases. Rings and bases sold separately; select the correct base set for your rifle, then choose rings. Those marked �Rev. Frt.� have reversible front base to help get correct ring spacing.