Ruger 10/22:
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.
Outside to outside of rings is 4.29″. Standard rings are .63″ wide and have 2 ring screws per ring. 4 Hole to hole spacing dimensions are .86″, 2.57″, .50″. Height of mounts from top of receiver to centerline of scope tube is – low .94″, medium 1.06″, and high 1.19″.