Diameter: 1/4inch (6.35mm), Accept Size: 1/4inch and 1/2inch , Extend Length: 2-1/4inch. This router collet extension chuck accepts both 1/4inch and 1/2inch 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- handle Design, for ER20 M Lathe Clamping Nut. High precision, stable performance. Extend your router bit to the full depth of cut, for both 1/4 inch and 1/2 inch router bits. Eliminate the dangerous temptation of withdrawing the from the collet, extend the bit to the full depth of cut. Place the router collet extension in the 1/4-inch router collet and the router bit in the extension collet and tighten both. This router collet chuck 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: 1 * 1/4inch handle extension rod 1 * ER20 1/4inch collet 1 * ER201/2inch collet 1 * ER20M wrench Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.