CHROME VANADIUM Steel - 31CrV3. Chrome plated, polished rings. Rings - thin walled with deep offset, UD profile. Same size on each end. Contents: 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8", 15/16", 1"