Hirobo HI2521123 4 x 5 x 4.3 Shaft Collar for RC Helicopter Assemblies  [HI2521123]

Shaft collar use in rotor assemblies

The Hirobo HI2521123 collar is a simple mechanical component denoted by its manufacturer code and dimensions, intended to hold parts at a defined axial position on a model helicopter shaft. It provides an axial stop or spacer so bearings, gears and linkages maintain their intended locations in the rotor assembly.

Fitment is simple: place the collar at the required position and secure it with the model's retention method or a compatible fastener. Because shaft sizes and mating parts vary, measure and dry-fit the collar to confirm proper clearance before final tightening.

Regular inspection will reveal if the collar has worn or shifted; replace it if you observe deformation or persistent slippage to keep axial alignment reliable and avoid downstream drivetrain or control problems.