Shank Diameter: 1/4 inch (6.35mm), Accept Shank Size: 1/4 inch and 1/2 inch Shank, Extend Length: 2-1/4 inch. This router collet extension chuck accepts both 1/4 inch and 1/2 inch shank router bits for converting and extending. Converter Adapter and ER20 Spring Collet made of durable steel for maximum strength and 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 provides the additional depth of cut needed for many routing tasks. Easy to use, better to control, it will improve your work efficiency. Color: silver Material: carbon steel Package Contents: 1 * 1/4 inch handle extension rod 1 * ER20 1/4 inch collet 1 * ER20 1/2 inch collet 1 * ER20M wrench Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to be slightly different from the real thing. The measurement allowed error is +/- 1-3 cm.