Professional design ideal for drilling square holes in wood with a mortiser. Fits all machines and drill attachments. Square hole drill bit is mainly used in woodworking field. Material and size: made of high speed steel. Heat treatment, high hardness, elongated center, high concentricity; 4 sizes 1/4' (6.35mm), 5/16' (7.94mm), 3/8' (9.5mm), 1/2' (12.7mm). Why choose this item: Reduces the labor intensity of construction workers while accelerating the speed of work and reducing costs. Perfect for the construction, renovation and decoration sectors. Scope of delivery: 1 piece 1/4'; (6.35mm), 1 piece 5/16" (7.94mm), 1 piece 3/8' (9.5mm), 1 piece 1/2' (12.7mm), Note: The punch square needs to use a drill, hammer or other tools. (None of these items are included). Features: 1. Professional wood drill bit, suitable for construction, installation, renovation, decoration, etc. 2. The part forms a hole drilled by the rotating body, while the impact of the use of the percussion force is transmitted to the outside of the body, the material created a round hole and a square head, in one go, and the dust can be discharged through the tube. 3. The dimension corresponds to the length of the square hole drilled. 4. The diameter of the cylinder of the clamping portion is 19 mm. 5. Drill hole center is over 210mm, for longer drill centers. Specifications: Sizes: 1/4&#34 ; (6.35mm), 5/16' (7.94mm), 3/8' (9.5mm), 1/2' (12.7mm). Materials: High-speed steel. DIY supplies: Woodworking. Use: Drilling/perforating wood. p> Package Contents: 1 x 1/4" or 6.35mm. 1 5/16" or 7.94mm. 1 3/8" or 9.5mm. 1 1/2" or 12.7mm. Note: Please allow 1-3 cm error due to manual measurement. Depending on monitor's brightness and lighting settings, the actual color of the item may be slightly different from the pictures. Thank you for your understanding.