1. Built in self-Release design and tools will never stuck in holder. 2. The metal collet nut has a strong clamping force and is not deformed. 3. Precision machine tool accessories grinding of this product may dust during using. Specification: Model: ER11-A Standard: Metric Thread Size: M14 Overall Size:19x14mm/ 0.75inchx0.55inch (D*H) Thread Pitch: 0.75mm / 0.03inch Hex Width: 17mm / 0.67inch Hole Diameter: 9mm/ 0.35inch Colour:Black Material:Steel Size:19x14mm Package Contents: 4 * Collet Clamping Nuts Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.