Comes with 1 square hole drill bit adapter and 5 square hole drill bits, drill diameter: 1/4 inch (6.4mm), 5/16 inch (8mm), 7/16 inch (11mm), 1/2 inch (12.7mm) 5/8 inch (16mm) and hand drill clamp diameters range from 38 to 55mm / 1.5 to 2.2 inch (. 5.9cm), easy to install and use; please note it only works with belts Clamps for bench drills and hand drills The square hole drill bit adapter is made of high-quality carbon steel, sturdy and , to hold wood firmly, the length of the drill bit adapter is about 6.3 inches/16 cm, the upper inner diameter is about 0.75 inches/1.9 cm, and the lower diameter is about 2.17 inches/5.5 cm to reduce usage errors, the specially designed tenon accessory drill bit not be blocked by the wood chip chip, wood chip chip, no rolling, fast cutting speed, drill bit, please take it out safely The drill bit adapter and 5 sizes of matching drill bit attachments are more convenient to use, and the precision design of the drill mortise attachment ensures you can