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- Mauser FN (also Browning FN .264 through .458, Harrington & Richardson 300, 301, 330 , 370 Pre-1973, J.C.Higgins Pre-1955, Marlin 455, Mauser M12, Mauser Mark X, Parker Hale 100, 1100, 1200, Remington Model798, Sako Round Receiver, and Weatherby FN).