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

Precision shaft collar for helicopter shafts

This Hirobo HI2521123 collar is an RC-scale shaft accessory identified by its manufacturer code and size marking, designed to locate and retain components along a model helicopter shaft. As a simple mechanical stop it provides a defined axial position so bearings, gears, linkages, or other small parts stay correctly placed during operation.

Installation is straightforward: slide the collar to the required spot on the shaft, then secure it using the model's existing retention method or a compatible fastener. Because kits vary, verify fit and clearance with adjacent rotating parts before final tightening to avoid interference.

In setup and tuning, collars like this are used to establish endplay, maintain correct gear mesh, and prevent linkages from shifting under load. Inspect periodically for wear or loosening and replace the collar if you detect deformation or ongoing slippage to preserve reliable axial positioning.