Item Type: Milling Shank Holder Material: 40cr alloy steel Model: NT30 ER20 Rear Drawing Thread: M12 Tail Aperture: Approx.12mm/0.5in Structure Type: Monolithic Accuracy: 0.003 Scope of Application: CNC machining centers, engraving machines and other high speed machines Package List 1 x Milling Shank Holder 1 x ER20A Wrench 1Vacuum Quenched: The collet chuck holder has been vacuum quenched, has high hardness, strong toughness, good fatigue, impact and load resistance 2Good Structural Rigidity: The milling shank holder is integrated formed, has good structural rigidity, the pressure is dispersed on the precise needle roller of the cage during use, suitable for large cutting amount processing 3Connection Protective: The collet chuck holder is fully ground as a whole, effectively protecting the connection of the taper hole of the power head 4Fine Grinding Processed: The external of the holder is brightly ground for beautiful and elegant appearance, the shank hole is fine grinding processed, with high centering accuracy 5Wear Resistance and Stable: The mill tool holder is made of high quality 40cr alloy steel, has better wear resistance and good stability