Sunwin Hollow CNC Rotational Hollow Shaft 4th Rotary Axis 4th Axis Router Rotational Er32 3-20mm Chuck a Axis for Engraving Machine A Axis ER32 Precision Spring Collet Set 3-20mm Chuck type: Standard ER32 collet 3~20mm (Hollow shaft) Reduction ratio: 6:1 (synchronous belt deceleration mode) Step motor: 57 phase stepper motor (two-phase 4 wire current 3A ) ER32collet:3mm,4mm,5mm,6mm,8mm,10mm,12mm,14mm,16mm,18mm,20mm(Please let us know which type you need)