Professional design, ideal for drilling square holes in wood with a mortiser. Compatible with all machines and drills. Square drill bits are mainly used for woodworking. Material and Dimensions: Made of high speed steel. Heat treatment, HRC48~50, high hardness, elongated center, high concentricity. 4 sizes: 1/4 inch (6.35 mm), 5/16 inch (7.94 mm), 3/8 inch (9.5 mm), 1/2 inch (12.7 mm). Why choose this product? Reduces the workload of construction workers while speeding up work and reducing costs. Ideal for construction, renovation and decoration. Package includes: 1 piece 1/4 inch (6.35 mm), 1 piece 5/16 inch (7.94 mm), 1 piece 3/8 inch (9.5 mm), 1 piece 1/2 inch (12.7 mm). Note: The punching square must be made at using a drill, hammer, or other tool. (None of these are included.)