Specification:Model: ER20 - 1/8UPMaterial: SUJ2Diameter: approx. 21mmInside diameter: 1/8Accuracy UP(grade): 0.005mmHardness: HRC511 Suitable for handle: BT30/BT40/BT50-ER Handle Features: Made of premium material, high strength and hardness, strong structure, durable in use. High quality ER20 collet block for CNC lathe engraving machine. High clamping force, more convenient clamping, faster replacement. Smooth surface, no scratches, stable performance. Widely used in milling, boring, drilling, tapping operations, suitable for all kinds of CNC, engraving machine, walking machine, punch machine, spindle equipment, etc.