1. Built in self-Release design and tools will never get stuck in holder.2. The metal collet nut has a strong clamping force and is not easily deformed.3. Precision machine tool accessories grinding of this product may produce dust during using.Specification:Model: ER11-AStandard: MetricThread Size: M14Overall Size:19x14mm/ 0.75inchx0.55inch (D*H)Thread Pitch: 0.75mm / 0.03inchHex Width: 17mm / 0.67inchHole Diameter: 9mm/ 0.35inchColour:BlackMaterial:SteelSize:19x14mmPackage Contents:4 * Collet Clamping NutsOnly 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.