Professional design ideal for drilling square holes in wood with a mortiser. Fits all drill machines and attachments. The square hole drill bit is primarily used in woodworking applications. Material and size: Made of high-speed steel with heat treatment, HRC4850 hardness for durability. Features an elongated center and high concentricity. Available in four sizes: 1/4" (6.35mm), 5/16" (7.94mm), 3/8" (9.5mm), and 1/2" (12.7mm). Benefits: Helps reduce labor intensity, increases work efficiency, and lowers project costs. Suitable for construction, renovation, and interior decoration applications. Package includes: One 1/4" (6.35mm) bit, one 5/16" (7.94mm) bit, one 3/8" (9.5mm) bit, and one 1/2" (12.7mm) bit. Note: A drill, hammer, or other driving tool is required for use. These tools are not included.