Features: Precision machined from a solid block of top grade billet 6061 T6 aluminum Custom made to fit each Type of firearm and align perfectly with your rifle's receiver No moving parts between the firearm and the scope 67% lighter than comparable one-piece mounts with four times the threads and precision socket-head cap screws for absolute strength and security Absorbs shock and withstands temperature extremes better than steel mounts at a fraction of the weight Base screws are #6-48 x 1/4 inches long and ring screws are #6-40 x 5/8 inches long, both screws use a 7/64 inches allen wrench Outside to outside of rings is 4.24 inches, rings are 0.63 inches wide, 4-hole to hole spacing dimensions are 0.50, 3.19, 0.50 inches Mount fits both left and right hand firearms Made in the USA