Weaver Aluminum Top Mount Base Gloss Number 12 Each base is machined to tight tolerances for a custom fit. Aluminum bases offer maximum strength for rings to hold tight Used as front base on: - Marlin 980 - Remington 550, 514 (Drilling and tapping may be required on the 514) - Stevens 57, 76, 417 1/2, 762 - Winchester 74 Used as rear base on: - Marlin 80, 81, 980 - Mossberg 25, 26, 42, 45, 46, 46a, 46, 46 with 13/16 diameter. 46M, 140, 142, 146, late models 45 and 46 with 3/4 diameter Bbls. - Remington 550, 514 (Drilling and tapping may be required on the 514) - Winchester 47, 57, 69, 69A, 72, 74