MR125-ZZ Ultra-Miniature Deep Groove Ball Bearing For Sensitive Instruments | 5×12×4 Mm
The MR125-ZZ is a Double-Shielded Ultra-Miniature Deep Groove Ball Bearing engineered for precision and reliability in extremely space-limited applications. Utilizing the fundamental deep groove raceway, this micro-sized bearing is capable of supporting light radial loads and minimal axial loads from both directions. With a compact 5 mm bore and pre-installed double metal shields (ZZ) for protection, it is a critical component for sensitive instruments, micro-motors, optical devices, and other applications where minimal size, smooth operation, and contamination resistance are paramount.
MR125-ZZ Deep Groove Ball Bearing 5x12x4 mm | Micro Series | Double Metal Shields (ZZ)
A precision micro-series bearing built with the standard deep groove geometry. Designed for stable and quiet operation at speeds up to 50,000 r/min (Grease). The MR125-ZZ provides reliable performance in a minimal footprint, making it an essential choice for high-precision, small-scale mechanical and electromechanical systems.

Designed for ultra-compact precision mechanisms and micro-drives:
Miniature DC Motor Spindles
Small Cooling Fan Motors (e.g., for chipsets)
The micro-series design delivers essential bearing functionality in one of the smallest standard form factors, with reliable radial load capacity for its size. Manufactured from high-grade chrome steel, it ensures dimensional stability and consistent performance in precision applications.
Comes standard with double metal shields (ZZ), providing a critical barrier against dust and fine particulate ingress. This design maintains very low rotational friction, making it ideal for maintenance-free, long-life applications.
Manufactured to fine tolerances standard for miniature bearings. The precision-ground components ensure exceptionally smooth, low-vibration, and quiet rotation, enabling reliable performance at very high rotational speeds.
| Bearing Type | Single Row Deep Groove Ball Bearing |
| ISO Dimension Series | MR Series – Micro Series |
| Basic Designation | MR125 |
| Suffix | Double Metal Shield (ZZ) |
| Bore Diameter (d) | 5 mm |
| Outer Diameter (D) | 12 mm |
| Width (B) | 4 mm |
| Material (Races & Balls) | Chrome Steel (GCr15 / SAE 52100) |
| Precision Class | Standard / P5 Grade Available |
| Cage Material | Stainless Steel or Pressed Steel |
| Dynamic Load Rating (Cʳ) | 0.78 kN |
| Static Load Rating (C₀ʳ) | 0.30 kN |
| Limiting Speed (Grease) | 50,000 r/min |
| Limiting Speed (Oil) | 63,000 r/min |
| Weight (approx.) | 2.5 g |
Direct replacement for:
The MR125-ZZ is supplied as a pre-lubricated and pre-shielded unit with double metal contact shields (ZZ). This configuration offers a sealed-for-life, maintenance-free solution with fundamental protection against contaminants. For prototype or special applications requiring an open design, custom orders may be available.
"For micro-motors, optical instruments, and any application where space is at an absolute premium, the MR125-ZZ provides a reliable, shielded bearing solution. Its ultra-compact size and integrated protection make it ideal for advanced miniaturized designs."
The MR148-ZZ is a Robust Miniature Deep Groove Ball Bearing engineered for applications that require dependable performance with enhanced protection from contaminants. Featuring dual steel shields (ZZ) on both sides, this metric bearing provides a solid barrier against dust and airborne particles, helping to retain internal lubrication and promote smooth, extended service life. With an 8mm bore, it is well-suited for integration into small electromechanical systems, precision equipment, and motor assemblies where space efficiency and reliable sealing are key priorities.
Details
The MR137-ZZ is a Miniature Double-Shielded Deep Groove Ball Bearing engineered for reliable performance in compact, precision applications. Utilizing the fundamental deep groove design, this small-diameter bearing is capable of supporting radial loads and very light axial loads in either direction. With a 7 mm bore and integrated double metal shields (ZZ) for basic contamination protection, it is an essential component for sensitive instruments, small motors, precision drives, and other applications where space is limited and smooth, low-friction operation is critical.
Details
The MR126-ZZ is an Ultra-Compact Double-Shielded Deep Groove Ball Bearing engineered for reliable performance in space-constrained precision applications. Featuring the standard deep groove raceway design, this miniature bearing efficiently handles radial loads and minimal axial loads from both directions. With a 6 mm bore and built-in double metal shields (ZZ), it provides essential protection while maintaining low friction, making it an ideal component for small electric motors, sensitive instruments, micro-drives, and other compact devices where smooth, maintenance-free operation is critical.
Details
The MR125-ZZ is a Double-Shielded Ultra-Miniature Deep Groove Ball Bearing engineered for precision and reliability in extremely space-limited applications. Utilizing the fundamental deep groove raceway, this micro-sized bearing is capable of supporting light radial loads and minimal axial loads from both directions. With a compact 5 mm bore and pre-installed double metal shields (ZZ) for protection, it is a critical component for sensitive instruments, micro-motors, optical devices, and other applications where minimal size, smooth operation, and contamination resistance are paramount.
Details
The MR117-2RS is an Ultra-Miniature Deep Groove Ball Bearing designed for applications where space is extremely limited and reliable sealing against contaminants is essential. Featuring double rubber contact seals (2RS) on both sides, this bearing provides superior protection against dust, moisture, and fine debris while maintaining smooth rotational performance. With a 7 mm bore and a compact 11×2.5 mm cross-section, it is ideal for micro motors, small instruments, precision mechanisms, and devices operating in challenging environmental conditions.
Details
The MR105 is a Miniature Deep Groove Ball Bearing designed for high-precision applications in compact assemblies where minimal friction and smooth operation are essential. With an open design (no seals or shields), this bearing offers unobstructed performance, making it ideal for clean environments, high-speed mechanisms, and applications requiring frequent re-lubrication. Featuring a 5 mm bore and compact 10×4 mm dimensions, it delivers reliable radial and axial load support in tight spaces.
Details
The MR128-2RS is a high-precision miniature ball bearing specifically developed for compact mechanical assemblies where internal clearances are tight and environmental protection is vital. Outfitted with dual contact rubber seals (2RS), this micro-bearing provides a superior barrier against fine dust and moisture while ensuring the internal lubricant remains stable during operation. With an 8mm bore, a 12mm outer diameter, and a slim 3.5mm width, it is the premier choice for RC racing components, small brushless motors, and precision dental tools requiring smooth, dependable rotation.
Details
The MR128-ZZ is a precision-engineered miniature ball bearing designed for high-velocity mechanical systems where low starting torque and minimal heat generation are essential. Featuring dual non-contact metal shields (ZZ), this micro-bearing provides reliable protection against larger debris while allowing the internal lubricant to operate at maximum efficiency. With an 8mm bore, a 12mm outer diameter, and a 3.5mm width, it serves as a critical high-performance component for cooling fans, high-frequency micro motors, and precision hobbyist electronics.
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