All S&K rings are fully machined out of solid steel bar stock, tumble finished to remove all burrs, and have a 3/8" diameter stud that locks into a 3/8" hole or slot in the base which provides windage adjustment. The rings are locked into position by tightening cooperative cone pointed set screws. The rings are precision bored diameter and, being machined rather than extruded or stamped, form a precision fit that will not slip under recoil. They are nicely contoured and trim in appearance. Rings are tumble finished and blued to achieve a military-type dull or nonglare black finish that matches the black anodized Insta-Mount bases. Bases need purchased separately.
Big Book Catalog, Issue:66, Page:258