Square Hole Drill Bit Set: Includes 1 square hole bit adapter and 4 square hole drill bits. Compatible with bench drills and hand drills with clamp diameters ranging from 38 to 55 mm (1.5 to 2.2 inches) for easy installation and use. Note that this product is only suitable for bench drills and hand drills equipped with clamps. Quality Materials: The square hole drill bit adapter is made of high-quality steel, ensuring strength and durability. It securely fixes wood and fits various mortise accessories. The cutting surface is precision-machined to reduce errors during use. Specially designed to prevent blockage by wood chips. High hardness, non-slip design, fast cutting speed, and sharp cutting edge. Handle with care when removing after use. Efficient and Accurate: The adapter works seamlessly with four included drill bit sizes for easier operation. The precise design of the mortise attachment ensures accurate and efficient drilling of square holes, offering a faster alternative to traditional mortise machines. Widely Applicable: This drill bit adapter helps reduce labor intensity and improves work efficiency. Ideal for construction, carpentry, DIY projects, and interior decoration. Suitable for use on low-hardness materials such as compressed board, plastic, MDF, sandalwood, pine, ash, and similar woods. Dual Support Bracket: The square hole drill bits are reliable and practical, compatible with both bench drills and hand drills. The adapter is ideal for woodworking, furniture manufacturing, and related applications. Note: Minor color variations may occur due to lighting or screen display differences. These do not affect product functionality. Thank you for your understanding. Material: Steel Color: As shown Package Contents: 1 x Square hole bit adapter 4 x Square hole drill bits Note: Light reflection and different displays may cause slight color differences between the image and the actual item. Measurement error allowed is +/- 1-3 cm.