Made of premium chrome vandium steel, size Includes ：6 mm x 7 mm, 8 mm x 9 mm, 10 mm x 11 mm, 12 mm x 13 mm, 14 mm x 15 mm, 16 mm x 17 mm, 18 mm x 19 mm, and 20 mm x 22 mm.        
Double box end construction ensures a secure grip on fasteners, reducing slippage and protecting bolt corners.        
To prevent damaging round-off, the geometry of each opening contacts and applies force to the flat sides of fastener heads rather than the corners.        
Constructed from high strength drop forged and heat treated chrome vanadium steel, Corrosion and rust resistant sand blasted and polished for durability and extended tool life.    Supplied with a roll-up canvas pouch for easy organization, portability, and quick size identification.