Weaver Top Mount Base Used On: Marlin 9, 45, 30AW/AS, 36, 62, 93, 336, 375, 444, 1893, 1894, 1895, Glenfield 30, Zane Grey, Camp 9 Carbine, 922M, 989, 22 Auto RFL, Mossberg 640. OCTAGON BARRELS OR FLAT TOP RECIEVERS (base length 4.700", .370" thick.)