Hirobo HI2521104 Precision Collar 3 X 6 X 12.5S for Helicopter Shafts  [HI2521104]

Helicopter Shaft Collar 3 x 6 x 12.5S

This collar is an RC-scale helicopter replacement part sold under the Hirobo designation HI2521104. It acts as a compact clamp used where a low profile collar is required on shafts or linkages in helicopter assemblies. The dimension label 3 x 6 x 12.5S identifies the nominal size for matching existing shafts and housings.

For installation, inspect the mating shaft and bore for wear or contamination, remove debris, and slide the collar into position before securing it with the original retaining method used on your model. Confirm fit and clearance prior to flight; even small alignment shifts can alter tail or rotor tracking on RC helicopters.

In tuning and routine service, collars like this provide precise axial location and limit lateral play in rotating systems. Regular fitment checks help keep rotor heads and tail assemblies running true, which supports stable trim and predictable handling on the model scale.