Complete Set with Robust Material:perfect achieving precise square holes, the adapter's robust construction ensures longevity and performance. Note: Protect from humidity with oil to maintain pristine condition. Compatibility and Installation Ease: Designed to fit benchtop drill presses and standard electric hand drills, the adapter supports a clamp diameter of 38-55mm (1.50-2.17 inches). It comes with a securing screw and a detailed assembly drawing for hassle-free setup and removal, enhancing both stability and ease of use. Efficiency and Precision: Equip your woodworking toolkit with this square hole drill bit adapter that guarantees precise and stable drilling results. The set includes four different sized drill bits (6.4mm/0.25 inch, 8mm/0.31 inch, 9.5mm/0.37 inch, 12.7mm/0.5 inch), catering to various project requirements. Tool Compatibility Advisory: This adapter is not suited for lithium battery-operated electric drills or bench drills lacking round hole bearings. It's optimal for traditional or household bench drills. Please confirm compatibility with your equipment before purchasing to ensure optimal usage. Practical Design for Professional Use: Ensure flawless execution of mortise and tenon joint tasks with our square drill bit adapter and bit set. Each component is designed for easy installation or disassembly, providing a swift and efficient workflow for both professional woodworkers and passionate DIY enthusiasts. Colour:Silver Material:steel Package Contents: 1x square hole drill bracket 4x drill bits 1x gadget 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.