Features 1、The collet is integrally formed with a long total length and is suitable for installation on a knife sharpener. 2、The clamping force is strong, and the clamping accuracy is 0.02mm, which is suitable for fine operation. 3、The accuracy of the aperture is high, the thread size is standard, and it is not easy to fall off during installation and use. 4、Different size specifications have different clamping ranges, which are suitable for different clamping situations. 5、Made of high-quality metal materials, the hardness is HRC40-45, and it is not easy to be squeezed by the outside world. Specification Item Type: Sharpener Chuck Model: 3-9mm Grinding Machine Chuck Hardness: HRC40-45 Clamping Accuracy: 0.02mm Clamping Range: Approx. 3mm / 0.12in, 4mm / 0.16in, 5mm / 0.2in, 6mm / 0.24in, 7mm / 0.28in, 8mm / 0.31in, 9mm / 0.4in Collet Total Length: Approx. 122mm / 4.8in Collet End Diameter: Approx. 20mm / 0.8in Tail Thread: M20 Tail Thread Length: Approx. 29mm / 1.1in Rod Diameter: Approx. 20mm / 0.8in Package List 1 x 7mm Chuck