With good quality, low noise and durable. All turbines are Dynamically balanced by Germany Balancing Machine. Air pressure at the back end of HP: 0.25-0.27Mpa(4 hole). 0.20-0.22Mpa(2 hole).Rotation speed: No less than 300,000rpm. Bur applicable: diameter 1.59mm -1.6mm. Work voltage: 3.0V -3.5V. All the items are inspected for damage or defects prior to leaving our warehouse. We accept the returne within 14 days after the item is received. Pls make sure the item is in original condition. Without this information, the return won't be processed. 510(K) Number: K181691 Regulation Number: 872.4200 Classification Product Code: EFB Subsequent Product Code: EGS.