RC Helicopter Shaft Spacer 4 x 5 x 4.3 for Setup - Hirobo HI2521123  [HI2521123]

Shaft spacer for model helicopter drivetrains

The Hirobo HI2521123 collar serves as a compact shaft spacer and axial stop for model helicopters, identified by its part code and measured dimensions. It secures bearings, gears and linkages in the intended positions to support predictable drivetrain behaviour.

To fit, slide the collar to the chosen axial location, then fasten with the model's retention method or a compatible screw. Always confirm clearance with rotating parts and verify gear mesh after installation to ensure proper operation.

When tuning, collars assist in fine-tuning endplay and gear alignment so the drivetrain runs smoothly. Check the collar during setup changes and replace it if you notice play or deformation that affects tuning results.