Armstrong Drive Socket, Deep Length, Measurement System Metric, 1/2 in Drive, Square Drive, 12 Point Socket, 18 mm Socket, 3.205 in Overall Length, 1.004 in Drive End Width, 1.004 in Socket End Width, 0.65 in Bolt Clearance Depth, 1.201 in Opening Depth, Ball Locking, High Alloy Steel, Chrome Plated