Made of premium quality high speed steel with high hardness and durability, anti-rust. These square drill hole bits are suitable for construction, installation, renovation,decoration industry, etc. Features: Made of premium quality high speed steel with high hardness and durability, anti-rust. Crushing round bits and square outer wall, broken slag dust can be discharged from the tube. Exquisite blade grinding process, edge is shar-per and more sturdy. Reduce labor intensity of construction workers and speed up the construction. Drilling square holes in wood with a mortising machine or a mortising attachment. Suitable for construction, installation, renovation, decoration industry, etc. Specifications: Clamping cylindrical diameter: 19mm Type: 9.5mm(3/8"),8mm(5/16"),12.7mm(1/2"),11mm(7/16") (optional) Drill core: 9.5mm(3/8"),8mm(5/16"),12.7mm(1/2"),11mm(7/16") (optional) Package size: 230 * 35 * 35mm Package weight: about 220g Note: 1. Please allow 1-3mm differs due to manual measurement. 2. Due to the different display and different light, the picture may not reflect the actual color of the item. Thanks for your understanding. 3. Square hole drill can not be used on an electric drill, drill square holes need to fit a square hole drill drilling (mortise and tenon machine) to use. 4. In case drill bits become overheated and get burned up due to fast rotary friction,we suggest use some cutting fluid to keep the bits cold during usage. Packing List: 1 * Square Hole Drill