MR52zz- MR149zz Mini Metal Double Shielded Small Ball Bearings Miniature Model

Measure three dimensions on your existing bearing or housing: bore diameter (inner hole), outer diameter, and width. The MR designation encodes these — for example, MR52ZZ has a 2 mm bore and 5 mm outer diameter. Use calipers for accuracy, then match to the type in the variant dropdown. If the housing is still assembled, consult the equipment's parts diagram or service manual for the bearing reference number.

ZZ indicates dual metal shields on both sides of the bearing. Shields block solid contaminants and retain grease but are not fully waterproof. For applications exposed to water spray or submersion, a rubber-sealed bearing (2RS designation) would provide better protection. For dry, indoor, or lightly dusty environments — such as 3D printers, RC cars, and robotics — ZZ shields are sufficient and allow slightly lower friction than rubber seals.

MR-series bearings are rated for light-to-moderate radial loads typical of hobby RC drivetrains, drone motor rotors, and small brushless motors. They are not designed for heavy axial (thrust) loads or high-impact shock loads. For standard RC wheel hubs, gearbox idler shafts, and motor end caps in the MR size range, these bearings perform within expected parameters. If your application involves sustained high RPM above 20,000 or significant axial loading, contact us to confirm suitability.

The steel races and shields can develop surface rust if exposed to prolonged moisture without protection. For outdoor RC use or humid workshop environments, apply a light coat of bearing grease or corrosion-inhibiting oil to the exterior after installation. The factory pre-grease inside the shields helps protect the balls and raceways during normal operation, but the outer surfaces benefit from periodic maintenance in wet conditions.

Yes. MR-series dimensions follow standardized conventions, so an MR84ZZ from this listing will have the same bore, outer diameter, and width as an MR84ZZ from other manufacturers. Verify the three key dimensions (bore, OD, width) against your original bearing before installing to confirm the fit, as minor tolerance variations between brands can affect press-fit tightness.

If you are replacing a bearing in an existing assembly for the first time, ordering 1 piece to confirm the fit and clearance is a practical approach. Once you have verified the correct type for your application, the 5- or 10-piece options offer a lower per-unit cost and keep spares on hand for future maintenance — useful for RC hobbyists running multiple vehicles or builders managing a fleet of 3D printers.