Stahlwille Series 40AD Bi-Hexagon sockets with 1/4in square drive in AF imperial sizes are made from HPQ® high performance steel, and are chrome plated. HPQ® sockets are manufactured from selected tough steel alloys for an extremeley high load capacity with exceptionally thin rings and walls. They are free of cadmium and are therefore suitable for use on titanium alloy parts and titanium fasteners, such as those used in the aerospace industry, where safety is a crucial factor. The Sockets are equipped with AS drives to permit high transmission of forces to the lands of the nuts and bolts without damaging them. Manufactured to ASME B 107.1, Fed. Spec. GGG-W-641, SAE AS 954-E (test loads). MADE IN GERMANY.Stahlwille Bi-Hexagon Socket 1/4in Drive. Size: 5/16 AF.Overall length: 23mm.