Shank Diameter: 1/4inch (6.35mm), Accept Shank Size: 1/4inch and 1/2inch Shank, Extend Length: 2-1/4inch. This router collet extension chuck accepts both 1/4inch and 1/2inch shank router bits for converting and extending. Converter Adapter and ER20 Spring Collet Made of durable steel for maximum strength and long life use; ER20 M Type Collet Chuck Wrench Spanner Made of High Carbon Steel, Anti-slip handle Design, for ER20 M Lathe Clamping Nut. High precision, stable performance. Extend your router bit to provide the full depth of cut, for both 1/4 inch and 1/2 inch shank router bits. Eliminate the dangerous temptation of withdrawing the shank from the collet, extend the bit to provide the full depth of cut. Place the router collet extension shank in the 1/4-inch router collet and the router bit shank in the extension collet and tighten both. This router collet chuck provide the additional depth of cut needed for many routing tasks. Easy to use, better to control, it will improve your work efficiency. Colour: silver Material: carbon steel Package Contents: 2 * 1/4inch handle extension rod 2 * ER20 1/4inch collet 2 * ER201/2inch collet 2 * ER20M wrench