Diameter: 1/4 inch (6.35 mm), Acceptable Sizes: 1/4 inch and 1/2 inch, Extended Length: 2-1/4 inch. This router collet extension chuck accommodates both 1/4 inch and 1/2 inch router bits for conversion and extension purposes. Converter adapter and ER20 spring collet are constructed from durable steel for enhanced strength and extended durability. The ER20 M type collet chuck wrench is made of high carbon steel with an anti-slip handle design, compatible with ER20 M lathe clamping nuts. High precision and stable performance allow for full depth of cut by extending your router bit, suitable for both 1/4 inch and 1/2 inch router bits. Helps prevent unsafe bit withdrawal from the collet. Insert the router collet extension into the 1/4-inch router collet, place the router bit into the extension collet, and securely tighten both components. Provides additional cutting depth required for various routing applications. Easy to use and improves control, enhancing overall 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 above are included; other products are not included. Note: Lighting and display differences may cause slight variations in the color shown in the image compared to the actual item. Measurement may vary by +/- 1-3 cm.