Hirobo HI2521102 RC Helicopter Shaft Collar 5 x 8 x 3.5 mm  [HI2521102]

Compact shaft collar for rotor drive components

This HI2521102 collar from Hirobo comes as a compact replacement listed under helicopter general parts and stamped 5 x 8 x 3.5. It is designed to act as a positional collar that locates and retains rotating shafts or spacers in model helicopter builds without asserting cross-compatibility beyond the manufacturer's general parts grouping.

During bench work, place the collar at the required axial point on the shaft and secure adjacent hardware to control endplay. As a small component, confirm the collar's dimensions match the target shaft and adopt the fastening procedure recommended by the helicopter's parts layout or maintenance documentation.

In tuning and upkeep the collar simplifies setting axial gaps between bearings or gears and helps re-establish consistent shaft alignment after service. Clean the part before use and confirm there is adequate rotational clearance to avoid binding within the transmission or rotor train.