These are for hand operation only and are available in ¼" to ½" square drive covering Bolt/Nut across flat sizes 4 to 34 mm ( ¼" to 1 3/8" SAE) and equivalent British Sizes. Heavy duty sockets are available in ¾" and 1" square drives covering across flat sizes from 19 mm to 85 mm (9/16" to 3 ½" SAE) and equivalent British sizes. These Heavy Duty Sockets are designed with a positive locking for its attachment with the driving tools having spring loaded ball & button. Deep sockets are also available to accommodate long studs.