Square Hole Drill Bit Set: Includes 1 square hole bit adapter and 4 square hole drill bits. Compatible with bench drills and hand drills featuring chuck diameters ranging from 38 to 55 mm (1.5 to 2.2 inches). Designed for easy installation and use. Intended only for bench drills and hand drills with chucks. Quality Materials: The square hole drill bit adapter is made of steel, offering strength and durability. It securely holds wood during operation and accommodates various mortise accessories. Precision-machined cutting edges help minimize operational error. The design helps prevent clogging by wood chips. High hardness ensures resistance to rolling and supports efficient cutting performance. Efficient and Accurate: The adapter works with four included drill bit sizes for versatile use. Precision engineering enables accurate mortise hole drilling. Offers a convenient and time-saving alternative to dedicated mortising machines. Widely Applicable: Helps reduce physical effort and improve work efficiency. Suitable for construction, carpentry, DIY projects, and interior decoration. Works well with low-hardness materials such as particle board, plastic, MDF, sandalwood, pine, ash, and similar woods. Dual Support Bracket: Square hole drill bits are reliable and practical for use with bench drills and hand drills. The adapter is ideal for woodworking, furniture manufacturing, and related applications. Note: Slight color variations may occur due to lighting conditions and display settings. These variations do not affect functionality. Measurement tolerance is ±1–3 cm. Material: Steel Color: As shown Package Contents: 1 x square hole bit adapter 4 x square hole drill bits Other items shown are not included.