Square Hole Drill Bit Set: come with 1 square hole bit adapter and 4 square hole drill bits, for bench drill and hand drill clamp diameters ranging from 38 to 55 mm/ 1.5 to 2.2 inches for easy installation and use Please note that it is only suitable for bench drill and hand drill with clamps Quality Materials: the square hole drill bit adapter is made of quality steel, strong and durable, can firmly fix the wood, drill machine mounting diameter of different mortise accessories, cutting surface is precision machined, reduce the use of error, specially designed with mortise bit accessories drill bit will not be blocked by wood chips, high hardness, no rolling, cutting speed, the bit is sharp, please take it out safely Efficient and Accurate: the bit adapter and the matching drill attachments in 4 sizes easier to use, and the precision design of the drill press mortise attachment ensures that you can drill the right mortise and mortise holes in the fastest way More convenient and faster than mortise machine Widely Applicable: this drill bit adapter can reduce labor intensity and improve work efficiency Appropriate for construction, carpentry DIY, decoration industry, which is suitable for compression board, plastic, density board, sandalwood, pine, ash, pine and other materials with low hardness Dual Support Bracket: square hole drill bits for wood are reliable and useful, suitable for bench drill and hand drill Square hole bit adapters are Perfect for woodworking, furniture manufacturing and other related industries. Please note: the physical slightly color difference or difference, does not affect the use, please do not mind, thank you! Material: steel colour: As shown Package Contents: 1 x square hole bit adapter 4 x square hole drill bits Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is 1-3cm.