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

Compact collar for micro helicopter shafts

This Hirobo HI2521107 collar is a compact shaft collar intended for RC helicopter maintenance and minor tuning tasks. The 3 x 5 x 5.1F dimension is the reference for matching the part to small-diameter shafts and related components.

Fitment advice: verify the receiving shaft accepts a 3 x 5 x 5.1F collar before installing, slide the collar to the required axial position, then secure it with the retaining method used on your model. The original source does not list material or hardness, so inspect the part on receipt or check the seller listing if material matters for your setup.

Use cases include trimming end clearance, stabilising linkages, and keeping gear meshes aligned where precise spacing is needed. Keep spare collars labelled by size to avoid swapping similar parts during field repairs.