Hirobo HI2521107 Shaft Collar 3 x 5 x 5.1F for RC Helicopter Tuning  [HI2521107]

Precision spacer for small helicopter shafts

The Hirobo HI2521107 collar is presented as a compact shaft location part for RC helicopters, identified by the 3 x 5 x 5.1F size code to help match it to small shafts. It functions to set axial position or act as a spacer between components where accurate spacing matters.

Installation: verify the shaft and assembly accept a 3 x 5 x 5.1F collar, slide it to the correct axial location, then secure using the model's compatible retention method. The original information does not specify material or hardness, so inspect the part on receipt or check with the vendor if material properties affect your setup.

In tuning scenarios the collar helps trim clearance, align gear meshes and stabilise linkages on rotor assemblies. Keep replacements organised by size codes to avoid fitting the wrong collar during repairs.