Diameter: 1/4 inch (6.35mm), Acceptable Bit Sizes: 1/4 inch and 1/2 inch, Extended Length: 2-1/4 inches. This router collet extension chuck is designed to accept both 1/4 inch and 1/2 inch router bits, providing conversion and extension capabilities. The adapter and ER20 spring collet are constructed from durable steel for enhanced strength and long-term use. 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. Offers high precision and stable performance. Extends the router bit to achieve full cutting depth for both 1/4 inch and 1/2 inch shank bits. Helps prevent unsafe bit slippage by ensuring secure bit installation. To use, insert the extension into the 1/4-inch router collet and place the router bit into the extension collet, then securely tighten both components. Provides additional cutting depth for a variety of routing applications. Easy to install and improves control during operation, 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 Note: The package includes only the items listed above. Other accessories shown are not included. Note: Lighting and display differences may cause slight variations in the color as seen on screen compared to the actual product. Measurement may vary by +/- 1-3 cm.