This simplified mounting system eliminates the possibility of an out of alignment interface or loose connection between the ring and base of traditional two-piece designs. Fully CNC machined from lightweight aircraft-grade aluminum to the industries tightest tolerances, this rigid scope mounting platform requires no lapping and is ready to go out of the box. *Note- Designed to fit Winchester Model 70 standard caliber action rifles with rear hole spacing of .860 inches. Standard calibers include but are not limited to: .223 Rem, .243 Win, 25-06 Rem, .264 Win Mag, .270 Win, .30-06 Springfield, .300 Win Mag, .308 Win and .338 Win Magnum.