Router Collet Extension for 1/4 Inch Bits, 1/2 Inch Bits, 8mm Shank Bits; Need to tighten with a wrench to prevent the bit from falling off. Made of heavy-duty steel for long life use, practical to use. Eliminate the dangerous temptation of withdrawing the shank from the collet, extend the bit to provide the full depth of cut. Make you more efficient to process products, suitable for woodworking trimming, milling, engraving machine. Easy to use, better to control, it will improve your work efficiency. Use it to achieve full depth of cut when machining dovetail splines, ideal for your woodworking.