Ruger American (centerfire):
Mount fits both left and right hand firearms.
Base screws are 6-48 X 1/4" long. Ring screws are 6-40 X 5/8" long. Both screws use a 7/64" Allen wrench.
Long action - Outside to outside of rings is 4.49". Standard rings are .63" wide and have 2 ring screws per ring. 4 Hole to hole spacing dimensions are .86", 3.54", .86". Height of mounts from top of receiver to centerline of scope tube is - low .92", medium 1.05", and high 1.17".