Deciding Between Two Bearing Types
When a machine needs new bearings, choosing between a rotary deep-groove ball bearing and a linear bearing can feel like comparing clamps to rails. The 8 Pcs 604ZZ set is made for small spinning shafts and appliance motors. The Industrial LM25UU 12-piece kit is built for smooth sliding on CNC guide rails. This head-to-head will help you pick the set that matches the way your equipment moves.
Quick Verdict
If your project uses small motors, gearboxes, power tools, fans, or household appliances with rotating shafts, the 604ZZ set gives you eight metal-sealed 4x12x4mm bearings at $17.75. If your work involves CNC rails, linear guides, or other sliding-axis setups, the LM25UU kit provides twelve 25x40x59mm linear bearings at $39.95. The bigger decision is motion type, not just price.
At a Glance
| Feature | 8 Pcs 604ZZ Deep Groove Ball Bearings | Industrial LM25UU Linear Bearings |
|---|---|---|
| Motion type | Rotating shaft support | Linear sliding motion |
| Bore / size | 4mm inner, 12mm outer, 4mm width | 25mm bore, 40mm outer, 59mm length |
| Pieces per set | 8 | 12 |
| Price | $17.75 | $39.95 |
| Typical use | Miniature gearboxes, small motors, appliances | CNC and linear motion systems |
Where Each Product Wins
- The 604ZZ set wins when your shafts are small and the movement is rotary; it is also the lower-priced set at $17.75.
- The LM25UU set wins when you need linear movement, a 25mm bore, and a dozen pieces to cover a longer rail; its $39.95 price includes a 1-year manufacturer warranty.
Product Notes
8 Pcs 604ZZ 4x12x4mm Deep Groove Ball Bearing Metal Sealed Industrial Bearing
This set gives you eight miniature metal-sealed ball bearings sized 4x12x4mm. That spec matches small shafts in gearboxes, remote-control cars, printers, fans, mixers, juice extractors, and treadmills, according to the product description. At $17.75, it is a low-cost way to refresh a handful of small rotating assemblies. The steel construction and polished race surfaces are intended for durable operation in high-cycle equipment, which makes the kit practical for appliance repair and hobby builds. The limitation is the size: a 4mm bore and 12mm outside diameter fit only small housings and shafts. If your equipment needs a 25mm bore or linear sliding motion, this set will not help. Choose it when the project calls for compact rotating bearings.
Industrial LM25UU Linear Bearings, 25x40x59mm, 12 Pieces CNC Compatible
This 12-piece linear bearing set is engineered for sliding motion rather than rotation. Each LM25UU has a 25mm bore, 40mm outside diameter, and 59mm length, and the set is described as CNC compatible. That makes it a match for linear guide rails on CNC machines and similar moving-axis builds. The optimized design gives a low friction coefficient and high rigidity, which helps keep motion smooth and stable during precise positioning. At $39.95, it costs $22.20 more than the 604ZZ set, but the larger size, twelve pieces, and one-year manufacturer warranty reflect a heavier-duty application. The trade-off is that it is not meant for small rotating shafts: the bore and length are designed for linear travel, so it will not replace a deep-groove bearing in a motor or gearbox.
Final Choice by Use Case
For a small rotating repair under $20, choose the 604ZZ set. For a linear-motion build with a 25mm bore, twelve-piece coverage, and a one-year warranty, choose the LM25UU set. If you are not sure which motion your machine uses, check whether the part slides along a rail or spins on a shaft; that answer points to the correct bearing type.
