Hirobo HI2521067 collar 4 x 5 x 6.5 mm RC helicopter shaft collar  [HI2521067]

Helicopter shaft collar 4×5×6.5

This collar is an RC-scale shaft component identified by its 4 x 5 x 6.5 marking and intended as a general-purpose part for model helicopters. It functions as a spacer and axial locator on small shafts where consistent spacing and repeatable blade position matter for rotor balance and control link geometry.

Fitment and installation are straightforward: slide the collar onto the shaft to the required position and secure according to the shaft and hub design used on your helicopter. The part’s nominal sizing is intended to match small rotor assembly interfaces; verify physical fit before final assembly to avoid interference with bearings or adjacent hardware.

In tuning and maintenance, this collar serves as a simple way to adjust blade tracking and maintain consistent head geometry after component changes. Keep spares for routine rebuilds and swapping during setup trials where millimetre-level spacing adjustments change rotor behaviour.