General description Router Collet Extension is designed for use with 1/4 inch, 1/2 inch, and 8mm shank bits, making it a versatile tool for various woodworking tasks, including trimming, cutting, and engraving. Technical specifications Includes: 1 x 1/4 Inch Router Collet Extension 1 x 1/2 Inch Router Collet Extension 1 x 8mm Router Collet Extension Installation Requires tightening with a wrench to secure the bit and prevent it from falling off during operation.