Hirobo HI2521016 Precision Ball Bearing Collar (A) 4 x 7 x 1.5 mm  [HI2521016]

Precision Collar for Small RC Bearings

This Hirobo ball bearing collar provides accurate axial positioning and spacing for small bearings used in model assemblies. The 4 x 7 x 1.5 designation specifies inner diameter, outer diameter and thickness so the collar matches bearing and shaft interfaces, and the part is identified as type "A" for precise placement rather than heavy load support.

In practice, the collar serves as a spacer and locator that sits against a bearing face or housing to limit endplay. Installation is straightforward on compatible shafts: slide the collar into position against the bearing or into its recess, then secure the surrounding hardware as your model's layout requires. Always confirm inner diameter and outer diameter match the mating bearing and shaft before fitting.

Small adjustments to collar position can change gear mesh and axial clearance in compact gearboxes and rotor assemblies. Use the collar to eliminate unwanted shaft movement and to reproduce consistent spacing when rebuilding small RC helicopters or micro drivetrains.