Sizes: #1 Spiral: 1/8-1/4″ (3-6mm), #2 spiral: 1/4-5/16″ (6-8mm), #3 spiral: 5/16-7/16″ (8-11mm), #4 spiral: 7/16-9/16″ (11-14mm), and #5 spiral: #5 spiral: 9/16-3/4″ (14-18mm). 1/4″ Hex for use with all corded and cordless drill drivers with 1/4″ hex or standard drill bit chucks.