The Leupold steel standard bases and rings are the most versatile of any mounting system we offer. The rear ring is secured by windage adjustment screws, allowing the scope's internal adjustments to be reserved for precise sight-in. Additionally, shims can be used for gross elevation adjustment, reserving the scope's elevation adjustment for bullet drop compensation dial applications. Fits- Winchester 70, 670, 770, & 70A (Short Action) Fits post war non-Express models (serial number higher than 66,360).