ZZ vs 2RS vs open bearings: which to use
Same size, different protection. Picking the right one decides how long the bearing lasts.
A 6203 ZZ, a 6203 2RS and an open 6203 are all 17 x 40 x 12 mm and fit the same shaft and housing. The only difference is what closes the gap between the inner and outer ring.
ZZ: metal shields
Two pressed steel shields that sit very close to the inner ring without touching it. Because nothing rubs, friction is very low and the bearing can run at high speed. Shields keep out dust and larger dirt but not water or fine slurry. Use ZZ in electric motors, fans, alternators and clean, dry places.
2RS: rubber seals
Two rubber seals that lightly touch the inner ring. They keep out water, mud and fine dust and keep the grease in, which makes 2RS the right choice for wheels, farm machines and anything washed or used outdoors. The rubbing seal adds a little friction and lowers the top speed slightly.
Open: no shield or seal
Open bearings are used inside gearboxes and engines where oil lubricates them. A shield or seal would stop the oil reaching the balls.
Quick choice
| Where it runs | Choose |
|---|---|
| Two-wheeler wheels, trailer wheels, farm equipment | 2RS |
| Electric motors, fans, alternators | ZZ (often with C3 clearance) |
| Inside an oil-lubricated gearbox | Open (or as originally fitted) |
| Dusty but dry, high speed | ZZ |
| Wet, muddy or washed often | 2RS |
Always replace like with like unless you know why the original type was chosen. See the full ball bearing range.
Frequently asked questions
Can I replace a 2RS bearing with ZZ?
It will fit, but a ZZ bearing lets water in. In wheels and wet places it will rust and fail early. Stay with 2RS there.
Can I remove a shield and regrease a ZZ bearing?
It is possible but not recommended. Shielded and sealed bearings are greased for life; replacing them is more reliable.
Need rates or stock?
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