The GRS ID (Inside Diameter) Ring Holder is installed in a bench vise or between the jaws of your engraving block. The ring holding system consists of a steel, L-shaped holder body and an array of 20 expanding plastic mandrels in 10 diameters (13.5 mm to 22.5 mm). A ring mounted on an expanding mandrel may be rotated while setting stones or engraving, or it may be locked in position without rotation. Furnished with additional accessories and instructions. Made in USA.