Chrome vanadium steel for strength and durability and precision broached jaws for sure gripping. Thin walled construction for access in cramped quarters and heat treated for consistent hardness. 12-point box end for snug fit. Meets ANSI standards.  Metric 11 piece set includes: 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 17 mm, 19 mm.