Historical
BS ISO 2725-3:2015
Assembly tools for screws and nuts. Square drive sockets. Machine-operated sockets ("non-impact") (British Standard)
ISO 2725-3:2015 specifies dimensions, designation, and marking of machine-operated "non-impact" square drive sockets.
NOTE Machine-operated "non-impact" square drive sockets are listed under number 301 in ISO 1703:1983.
British Standards Institution [bsi]