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 it is only suitable for bench drills and hand drills with clamps. Quality Materials: The square hole drill bit adapter is made of steel, strong and durable, designed to firmly secure wood and fit various mortise accessories. The cutting surface is precision machined to reduce errors during use. Specially designed to prevent blockage from wood chips. Features high hardness, no rolling, fast cutting speed, and a sharp bit edge. Handle with care when removing. Efficient and Accurate: The bit adapter and included drill bits come in 4 sizes for easier operation. The precision design ensures accurate mortise hole drilling, offering a faster and more convenient alternative to traditional mortise machines. Widely Applicable: This drill bit adapter helps reduce labor intensity and improve work efficiency. Suitable for construction, carpentry, DIY projects, and decoration applications. Works well with low-hardness materials such as compressed board, plastic, particleboard, sandalwood, pine, ash, and similar woods. Dual Support Bracket: Square hole drill bits are reliable and practical, compatible with both bench drills and hand drills. Ideal for woodworking, furniture manufacturing, and related fields. Note: Minor color variations may occur due to lighting or screen differences. This does not affect 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 Only the above items are included. Other products are not part of this package. Note: Lighting reflections and display settings may cause slight color differences between the image and the actual item. Measurement error allowance is +/- 1-3 cm.