Feature:1. Stable Performance: The router bit collet uses it to achieve the full depth of cut when processing dovetail splines, which is very suitable for a variety of woodworking.2. High Quality Materials: This chuck is made of industrial grade materials, with high accuracy, sturdiness and durability, and long service life.3. Easy To Use: Put the router bit collet extension handle into the router bit collet, put the milling cutter drill bit handle into the extension chuck, and tighten the two.4. Good Packaging: Each chuck is marked with a size and is well packed in a separate protective container with a label, so it is easy to distinguish them.5. Wide Range Of Applications: These kits are suitable for boring, milling, drilling, tapping, engraving, CNC, spindle machine tools and other processing.Specification:Item Type: Router Bit Extension Rod Material: Carbon SteelExtension Rod Total Length: Approx.85mm / 3.35inExtension Rod Outer Diameter: Approx.28mm / 1.10inNut Diameter: Approx. 28mm / 1.10inNut Height: Approx. 20mm / 0.79inER20 13 Collet:Height: Approx.32mm / 1.26inOuter Diameter: Approx.20mm / 0.79inInner Diameter: Approx. 13mm / 0.51inER20 6.5 Collet:Height: Approx.32mm / 1.26inOuter Diameter: Approx.20mm / 0.79inInner Diameter: Approx.6.5mm / 0.26inApplication: These kits are suitable for boring, milling, drilling, tapping, engraving, CNC, spindle machine tools, etc..Package List:1 x ER20M Nut2 x ER20 Collet1 x 1/2in Shank Extension Rod1 x WrenchNote:1. Please allow 1‑2in error due to manual measurement. Thanks for your understanding.2. Working speed too fast will cause the handle to be bent by excessive force.