Shank Diameter: 1/4 inch (6.35mm), Accepts 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 long life use. ER20 M type collet chuck wrench spanner made of high carbon steel with anti-slip handle design, compatible with ER20 M lathe clamping nut. High precision and stable performance. Extends your router bit to provide full depth of cut for both 1/4 inch and 1/2 inch shank router bits. Helps eliminate the risk of bit withdrawal from the collet during operation. Insert the router collet extension shank into the 1/4-inch router collet and the router bit shank into the extension collet, then tighten securely. Provides additional depth of cut needed for various routing tasks. Easy to use and improves control, enhancing work efficiency. Color: Silver. Material: Carbon steel. Package Contents: 1 x 1/4 inch handle extension rod, 1 x ER20 1/4 inch collet, 1 x ER20 1/2 inch collet, 1 x ER20M wrench. Only the items listed are included; other products are not included. Note: Lighting and display differences may cause slight variations in color between the image and actual item. Measurement may vary by +/- 1-3 cm.