Shank Diameter: 1/4inch (6.35mm), Accept Shank Size: 1/4inch and 1/2inch Shank, Extend Length: 2-1/4inch. This router collet extension chuck accepts both 1/4inch and 1/2inch shank router bits for converting and extending. High , stable performance. Extend your router bit to provide the full depth of cut, for both 1/4 inch and 1/2 inch shank router bits. Converter Adapter and ER20 Spring Collet Made of steel for maximum strength and use; ER20 M Type Collet Chuck Wrench Spanner Made of High Carbon Steel, Anti-slip handle Design, for ER20 M Lathe Clamping Nut. the dangerous temptation of withdrawing the shank from the collet, extend the bit to provide the full depth of cut. Place the router collet extension shank in the 1/4-inch router collet and the router bit shank in the extension collet and tighten both. This router collet chuck provide the additional depth of cut needed for many routing tasks. Easy to use, better to control, it improve your work efficiency., Weight: 0.64374980504 Pounds, Manufacturer: rirue