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: 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, strong and durable, providing a secure hold for wood drilling. The mounting diameter is precision-machined for reduced error during use. Specially designed to prevent blockage from wood chips. Features high hardness, no slippage, fast cutting speed, and a sharp cutting edge. Handle with care when removing after use. Efficient and Accurate: The adapter works seamlessly with four included drill bit sizes for improved usability. The precision design ensures accurate mortise hole drilling, offering a faster and more convenient alternative to traditional mortise machines. Widely Applicable: Helps reduce labor intensity and improve work efficiency. Ideal for construction, carpentry, DIY projects, and interior decoration. Suitable for use on low-hardness materials such as particle board, plastic, MDF, sandalwood, pine, ash, and similar woods. Dual Support Bracket Design: Provides stability and reliability during operation. Suitable for use with bench drills and hand drills. Ideal for woodworking, furniture making, and related applications. Note: Minor color variations may occur due to lighting and display differences. These do not affect product performance. 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. Measurement error allowed is +/- 1-3 cm. Only the items listed above are included.