These Faithfull Long Armed Hexagon Keys are made from fully hardened chrome vanadium and are ideal for driving socket screws. They are frequently used on machinery when securely fastening parts together and can also be used on domestic appliances and cycles. Faithfull keys from 4mm (5/32in) upwards have chamfered edges to prevent damage to fittings and keys from 3mm (1/8in) upwards are marked with their size. Ref: UTTK11139