Shank Diameter: 1/4 inch (6.35 mm), Accepted Shank Size: 1/4 inch and 1/2 inch shank, Extension Length: 2-1/4 inch. Router collet extension chuck accepts 1/4 inch and 1/2 inch shank router bits for conversion and extension. ER20 Converter Adapter and Spring Collet Made of steel for maximum strength and long service life; ER20 M type collet chuck wrench made of high carbon steel, non-slip handle, for ER20 M lathe collet nut. High precision, stable performance. Extend your router bit to provide the full depth of cut, for 1/4-inch and 1/2-inch shank router bits. Eliminate the dangerous temptation to remove the shank from the collet, extend the bit to provide the full depth of cut. Place the router collet extension shank into the 1/4-inch router collet and the router bit shank into the extension collet and tighten the two. Router collet chuck provides the additional depth of cut needed for many routing tasks. Easy to use, better to control, it will improve your work efficiency. Color: