Professional collet extension: use with any 8mm tool holder to give you the cutting height you need. STRONG AND DURABLE: The short, thick body is made of fatigue-resistant steel and is balanced and machined to eliminate the deflection seen with other extensions. Easy and convenient to use: Use the wrench to quickly change the tools above the workbench. No need to search for a spindle lock or use a wrench to change drill bits. Tip: Only 8mm shank cutters are accepted. Need to tighten with a wrench to prevent the drill bit from falling Note: The data are all manual measurements, please allow 1 - 3cm error, due to the difference in light and temperature. display, there will be a certain color difference, depending on the physical object received Delivery quantity: (according to the main picture)