Stem Diameter: 8mm, holding diameter: 8mm; Overlength: (77mm)Strong, sturdy and durable steel router collet extension for long life Eliminate the dangerous temptation to remove the collet shank, extend the bit to provide the full depth of cut Make you more efficient in processing products , suitable for wood cutting, milling, engraving machine The router extension chuck shank extends your router bits an additional 57mm, please note: Fits 8mm router bits only!Note:A. Please note that the extension rod should be securely fastened, but the chuck nut should only be tightened with the same pressure as any router chuck.B. This item needs to be installed in place and the working speed should be slow for normal use. The working speed is too fast and will cause the rod to overload and bend. Features:-This collet extender is made of industrial grade material, high precision, strong and sturdy for long life - It allows you to change router bits over the table, even without a lift! Even if you have an elevator, it still makes bit changes easier and you won't have to remove the insert ring. - Ideal for custom router tables with extra thick decks, it provides the extra depth of cut needed for many routing tasks. Specifications: Shank diameter: 8mm Holding Diameter: 8mm Overall Length: (77mm) Content:1 x 8mm Router Clamp Extension Note: The data are all manual measurement, please allow 1-3cm error, due to the difference of light and d display, there will be some color difference, depending on the physical object received.