DNZ Game Reaper Ruger 10/22 Medium Base Mount Matte Black - 1 Piece - Mount fits both left and right hand firearms. Base screws are 6-48 X 1/4in long. Ring screws are 6-40 X 5/8in long. Both screws use a 7/64in Allen wrench. Outside to outside of rings is 4.29in. Standard rings are .63in wide and have 2 ring screws per ring. 4 Hole to hole spacing dimensions are 0.86in, 2.57in, 0.50in.