This part of ISO 2725 specifies dimensions , designation and marking of machine operated "non-impact" square drive sockets. NOTE 1 : Machine operated "non-impact" square drive sockets are listed under number 301 in ISO 1703:1993 NOTE 2 : Hand operated sockets are dealt with in ISO 2725-1. Machine-operated "impact" sockets are dealt with in ISO 2725-2 .