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When a build demands reliable rotation in a confined envelope, undersized or mismatched bearings cause premature wear, wobble, and costly rework. Engineers, hobbyists, and repair technicians working on RC vehicles, 3D printers, robotics, and precision instruments need mini deep groove ball bearings they can trust to spec — every time.
This listing covers the MR-series mini deep groove ball bearings with double steel shields (ZZ), spanning sizes from MR84ZZ (4×8×3 mm / 0.157"×0.315"×0.118") through MR148ZZ (8×14×4 mm / 0.315"×0.551"×0.157"). Races and balls are manufactured from bearing steel with a hardened raceway, and the double-shield (ZZ) configuration keeps contaminants out while retaining factory grease lubrication.
Typical applications include 3D printer carriage and extruder assemblies, RC car and drone motor shafts, small servo mechanisms, CNC spindle supports, and medical or laboratory instrument pivots — anywhere a compact, low-friction rolling element is required in a metric MR-series footprint.
Both sides sealed with pressed steel shields to block dust, swarf, and debris while retaining factory-applied grease — no additional sealing required for most dry or lightly contaminated environments.
Races and rolling elements machined from bearing-grade steel with hardened raceways, delivering consistent load capacity and dimensional stability across the full MR84ZZ–MR148ZZ size range.
Each size conforms to standard MR-series metric tolerances (ID 4–8 mm, OD 8–14 mm, width 2.5–4 mm), enabling direct drop-in replacement in existing bearing seats without modification.
The deep groove geometry accommodates both radial and moderate axial loads in either direction, making these bearings suitable for combined-load applications such as motor shafts and lead-screw supports.
Available in 1 Pc, 4 Pcs, and 10 Pcs options per size — order a single bearing for a one-off repair or a 10-pack for batch builds and spares inventory.
Eleven distinct MR-series sizes in one listing (MR84ZZ through MR148ZZ) let you consolidate sourcing across multiple projects without managing separate product pages.
| Bearing Type | Deep Groove Ball Bearing, Double Shield (ZZ) |
|---|---|
| Series | MR (Miniature Metric) |
| Size Range (ID × OD × Width) | 4×8×3 mm — 8×14×4 mm (see variant options for exact size) |
| Available Sizes | MR84ZZ, MR85ZZ, MR95ZZ, MR104ZZ, MR105ZZ, MR106ZZ, MR117ZZ, MR126ZZ, MR128ZZ, MR137ZZ, MR148ZZ |
| Inner Diameter (ID) | See variant options |
| Outer Diameter (OD) | See variant options |
| Width | See variant options |
| Material | Bearing Steel |
| Shield Configuration | Double Steel Shield (ZZ) |
| Lubrication | Factory-applied grease (pre-lubricated) |
| Load Direction | Radial + moderate axial (both directions) |
| Pack Quantities | 1 Pc / 4 Pcs / 10 Pcs |
Match the bearing designation to your shaft diameter (ID), housing bore (OD), and available axial space (width). For example, if your shaft is 5 mm and your housing bore is 10 mm with 4 mm of axial space, select MR105ZZ (5×10×4 mm). Always measure your existing bearing or housing seat before ordering — do not rely solely on part numbers from different manufacturers, as tolerances can vary slightly.
ZZ bearings have pressed steel shields on both sides of the raceway. This keeps contaminants out and retains grease, making them suitable for most dry or moderately dusty environments without additional sealing. Open bearings have no shields and are easier to re-lubricate but require external sealing in dirty environments. Single-shield (Z) bearings protect one side only. These listings are ZZ only and are not interchangeable with open or Z variants of the same designation.
MR-series ZZ bearings are well-suited for moderate-to-high speed radial applications. The double steel shield does introduce slightly more drag than an open bearing at very high RPM, but for typical RC motors, 3D printer steppers, and small CNC spindles operating within the bearing's rated speed range, performance is reliable. If your application exceeds the rated speed for a given size, contact us to confirm suitability.
Deep groove ball bearings can accommodate moderate axial loads in addition to their primary radial load capacity. They are not designed as dedicated thrust bearings. For applications where axial load is the dominant force — such as vertical shaft arrangements under heavy thrust — a dedicated thrust bearing or angular contact bearing would be more appropriate. For combined radial and light axial loads (e.g., lead screws, motor shafts), these bearings perform well.
No. These bearings are pre-lubricated with grease at the factory and sealed by the double steel shields. They are ready to install as received. Do not wash or re-lubricate ZZ-shielded bearings with solvent-based cleaners, as this can flush out the factory grease and damage the shields. If re-lubrication is eventually needed after extended service, carefully remove one shield, apply a small amount of compatible bearing grease, and re-seat the shield.
Yes. The MR-series is one of the most common miniature bearing standards used in 3D printers (carriage rails, extruder idlers, Z-axis lead screws) and RC vehicles (wheel hubs, motor shafts, differential outputs). Check your printer or vehicle's service documentation for the specific bearing designation required, then select the matching size from the variant options above.
The MR prefix denotes a miniature metric series with non-standard dimensions smaller than the ISO 6xx series. For example, MR84ZZ (4×8×3 mm) has an 8 mm OD, whereas the smallest common 6xx bearing (608ZZ) has a 22 mm OD. MR-series bearings are designed specifically for compact mechanisms where standard 6xx bearings would not fit. They are not interchangeable with 6xx-series bearings of similar bore size.
