TPS TSR Low Sporting Optic Rings (.925), 30 mm The Most Precision Scope Rings On The Planet. Ring bore diameter circularity (roundness) within 2/10000 of a thousands. Ring bore parallelism and perpendicularity to ring base less than 1/10000 of a thousands. Direct supplier to to Canadian Defence Ministry for the C14 Timberwolf .338 Lapua (MRSWS) Manufactured in the United States by U.S. Veterans from 7075-T651 Aluminum Alloy