AQUSYZE, guaranteed accurate US sizes. With ring blank gauge. allows the craftsman to accurately calculate the length of a ring blank to create a definite ring size. Case hardened, hard chromed , stainless steel ( Rockwell 15-16) DEEP laser engraved markings. Stainless Steel ring mandrel produced to the absolute highest standards. Graduated with USA sizes from size 1 through size 16 in 1/4 size increments. Used by bench jewelers with a hammer or mallet for forming and shaping rings. Un-grooved. Sizes are EXACT USA ring standard.