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: suitable only for bench drills and hand drills with clamps. Quality Materials: the square hole drill bit adapter is made of high-quality steel, strong and durable, designed to securely fix wood and fit various mortise accessory mounting diameters. The cutting surface is precision-machined to reduce operational error. Specially designed to prevent blockage from wood chips during use. High hardness, non-slip, fast cutting speed, and sharp cutting edge. Handle with care when removing. Efficient and Accurate: the bit adapter and included 4 drill bit attachments are precisely engineered for quick and accurate mortise drilling. The design ensures efficient performance, making it more convenient and faster than 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 particleboard, plastic, MDF, sandalwood, pine, ash, and similar woods. Dual Support Bracket: square hole drill bits for wood are reliable and functional, compatible with bench drills and hand drills. The square hole bit adapter is ideal for woodworking, furniture manufacturing, and related applications. Note: slight color variations may occur due to lighting and display differences. This does not affect product performance. Material: steel Color: as shown Package Contents: 1 x square hole bit adapter 4 x square hole drill bits Note: only the items listed above are included. Other items are not part of this package.