Precision machined from a solid block of top-grade billet 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; Mount fits both left and right hand firearms; Receiver is rounded on front and back of receiver where mounts attach; Base screws are 6-48 x 1/4" long and ring screws are 6-40 x 5/8" long; Both screws use a 7/64" Allen wrench; Made in the USA