Contains 1/2", 3/8", and 1/4", with 1 standard post and 1 deep post in each size, providing a wide range of storage space Metric: (1) 1/2" drive, 10 mm-27 mm; (1) 3/8" drive, 6 mm-20 mm; (1) 1/4" drive, 4 mm-15 mm Made of heavy-duty molded ABS plastic with a stable, wide base for easy use in the workshop Each vertical pillar is marked with letters to distinguish between the different socket sizes