Complete Set with Robust Material:perfect achieving precise square holes, the adapter's robust construction ensures 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 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