7 Sizes Drill Bits with Adapter: includes 7 different sizes of square hole drill bits, namely 1/4 inch, 5/16 inch, 3/8 inch, 1/2 inch, 9/16 inch, 5/8 inch, and 3/4 inch, to meet your varying needs, as well as 1 piece of square hole drill bit adapter; Use different sizes of square hole drill bits, matched with the appropriate power of the square hole drilling machine, you can drill square holes to meet your requirements Square Hole Drill Bits: crafted from quality bearing steel, these mortise chisel drill bits boast an extended core, incisive cutting edges, and continuous blade; Such construction ensures rapid cutting and a firm fixation on the wood; The set is only for open square holes and locking drills, square hole drill bits cannot be applied on electric drills and bench drills; It requires the installation of a square hole drill (mortising machine) to drill square holes Square Hole Drill Bit Adapter: this square drill bit adapter is constructed from all steel casting, ensuring durability; With its length of 6.3 inches, 0.75 inch top inner diameter, and 2.17 inch bottom diameter, the adapter reduces the usage error, providing a more precise drilling performance Efficient Combination: the adapter is compatible with all the different sized mortise drill bits for wood, whether you are a beginner or an expert, each drill bit is designed to drill precise holes with minimal pressure, significantly reducing the stress on the operator and enhancing work efficiency, bringing much convenience in construction, installation, and decoration industries Widely Applied: these square mortise drill bits with adapter are perfect for both DIY enthusiasts and skillful workers, suiting well for construction as well as woodworking; They are suitable for lower hardness materials, including compressed board, plastic, density board, sandalwood, and so on; This makes it applicable for various sectors including DIY woodworking, construction, and decoration Features: This square hole drill bit set simplifies your work process as it is easy to assemble and disassemble. You can quickly install or remove the drill bits yourself, saving you both time and energy. These mortise drill bits for wood suit well from building furniture, joining wooden pieces, to an array of other woodworking, which will be a reliable tool in hand. Notes: Please confirm the size before purchasing. Pointed items are included, please be careful when using, and please keep them away from kids. Material: Bearing steel Color: Silver Package Contents: 7 x square hole drill bits (1/4inch/6.4mm, 5/16inch/8mm, 3/8inch/9.5mm, 1/2inch/12.7mm, 9/16inch/14mm, 5/8inch/16mm, 3/4inch/19mm) 1 x square hole drill bit adapter 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.