Marlin 1894, 1895, 336, XLR: Mount fits both left and right hand firearms. Base screws are 8-40 X 1/4″ long. Ring screws are 6-40 X 5/8″ long. Base screws use a 9/64″ Allen wrench and ring screws use a 7/64″ Allen wrench. Outside to outside of rings is 4.08″. Standard rings are .63″ wide and have 2 screws per ring. 6 Hole to hole spacing dimensions are .50″, 1.88″, .50″, .37″, .50″. Mount has 6 holes thru it so it can be used on the long and short receiver. 2 holes will not be used. Depends on the gun to what 4 will be used. Height of mount from top of receiver to centerline of scope tube is – medium 1.06″, high 1.19″.