Shank Diameter: 1/4 inch (6.35 mm), Accepts Shank Sizes: 1/4 inch and 1/2 inch, Extended Length: 2-1/4 inches. This router collet extension chuck accepts both 1/4 inch and 1/2 inch shank router bits for conversion and extension. Converter adapter and ER20 spring collet made of durable steel for strength and long-term use; ER20 M-type collet chuck wrench made of high-carbon steel with anti-slip handle design, compatible with ER20 M lathe clamping nut. High precision and stable performance. Extends router bit reach to achieve full depth of cut for both 1/4 inch and 1/2 inch shank router bits. Helps avoid unsafe practice of over-extending the bit shank from the collet. Insert the extension shank into the router’s 1/4-inch collet and the router bit shank into the extension collet, then tighten both securely. Provides additional cutting depth required for various routing applications. Easy to use and improves control and efficiency. Color: silver Material: carbon steel Package Contents: 1 × 1/4 inch extension rod 1 × ER20 1/4 inch collet 1 × ER20 1/2 inch collet 1 × ER20 M wrench Note: Color appearance may vary slightly due to lighting and screen settings. Measurement tolerance: ±1–3 mm.