The Precision Hardened Stainless Steel Main Shaft is made of hardened stainles steel and precision grounded. The Precision Hardened Stainless Steel Main Shaft is designed to replace stock main shaft and greatly reduces the chance of bending main shaft which may cause wobbling or head vibration. It is made to improve the head performance on Esky Honey Bee King and Cool helicopters. This hardened stainless steel main shaft is also grounded by CNC machines to make sure it is perfectly straight so the head does not vibrate under high speed rotation. It is much stronger than regular stock steel shafts and precisely drilled and milled with flat spots for maximum set screw grips.