Professional design ideal for drilling square holes in wood with a mortiser. Fits all machines and drill attachments. The square hole drill bit is mainly used in the woodworking field. Material and Size: Made of high speed steel. Heat treatment, HRC48~50, 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 work speed and reducing costs. Perfect for the construction, renovation and decoration sectors. Package Contents: 1 pc 1/4" (6.35mm), 1 pc 5/16" (7.94mm), 1 pc 3/8" (9.5mm), 1 pc 1/2" (12.7mm), Note: The punch square needs to use a drill, hammer or other tools. (None of these are included).