Hirobo HI2521016 Ball Bearing Collar Type A 4 x 7 x 1.5 mm  [HI2521016]

Micro Bearing Spacer Details

This Hirobo ball bearing collar is designed to control axial placement and spacing for small bearings in model builds. The 4 x 7 x 1.5 marking denotes ID, OD and thickness so the collar matches the bearing and shaft interface, and the item is catalogued as collar type "A" intended for positioning rather than bearing heavy loads.

Functionally, the collar acts as a spacer that sits against a bearing face or housing to restrict axial movement. Fitting is simple: position the collar against the bearing or into its recess on the shaft, then tighten surrounding hardware as required by your model. Always verify that inner and outer diameters match the mating bearing and shaft before installation.

During tuning and service, moving the collar slightly can affect gear engagement and axial clearance in small geartrains and rotor setups. Use the collar to remove unwanted shaft play and to recreate consistent spacing when rebuilding micro drivetrains or small rotorheads.