Material: high speed steel; hardness: HRC48-50, durable and practical, heat treatment, long service life. 4 different sizes: 1/4 (6.35mm), 5/16 (7.94mm), 3/8 (9.5mm), 1/2 (12.7mm). Ideal for drilling square holes in wood with a mortiser or mortiser. It is used in conjunction with the mortising machine. If you open the square hole manually, tools like a hand drill and hammer are needed. Standard chip design, easy to remove wood chip side, improve drilling efficiency. Reduces the labor intensity of construction workers, accelerates the speed of construction, reduces construction costs for construction, installation, renovation, decoration industries.