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 mortising machine or mortiser. It is used in conjunction with the mortising machine. If you open the square hole manually, tools such as a hand drill and a hammer are required. Standard chip design, easy to remove the side of the wood chips, improve drilling efficiency. Reduces the labor intensity of construction workers, accelerates the construction speed, and reduces construction costs for construction, installation, renovation, and decoration industries.