Hirobo HI2521125 Shaft Collar 3 x 4-6 x 15.5  [HI2521125]

Shaft collar for model helicopters

This collar is made for RC helicopter use where a 3 x 4-6 x 15.5 collar is required. It serves as a spacer and alignment element in compact mechanical assemblies, setting axial position on shafts and keeping consistent spacing between rotor or transmission parts.

Installation varies by the host model's fastening style; the part generally slides onto the shaft and is fastened by the model's existing clamp or screw system. When replacing or adjusting, verify shaft diameter and mating fit before final assembly to prevent play that could upset rotor balance or drive smoothness.

For maintenance and setup, the collar helps fine tune axial clearance and repeatably locate gears, hubs, or linkages during reassembly. It provides a stable reference so pitch, tracking, and drive engagement adjustments remain consistent across runs.