The 5-3/8″ Kirkland clamp/holder clamps from the outside for filing, polishing and stone setting and can also be used to clamp other jewelry. Unlike most clamps, it can also hold rings from the inside for total circumference polishing and buffing. The metal construction of high strength aluminum alloy conducts heat away from the ring. Holds ring sizes 1–13. Maximum opening 14mm. Made in the USA. Lifetime guarantee.