ZZ or 2RS? Choosing between shielded and sealed bearings
Two bearings, same size, different letters. Here is what ZZ and 2RS actually change, and how to choose the right one for your machine.
“Do you want it ZZ or 2RS?” We ask this question many times a day. Both keep grease in and dirt out, and both are packed with grease for life. The difference is how they do it, and that decides where each one belongs.
ZZ: metal shields
A ZZ (also written 2Z) bearing has a thin pressed-steel shield on each side. The shield is fixed to the outer ring and stops just short of the inner ring. It does not touch the rotating part.
- Low friction, so it runs cooler.
- High speed, usually the same speed limit as an open bearing.
- Keeps out larger particles, but not water or fine dust.
2RS: rubber seals
A 2RS bearing has a rubber seal, usually nitrile (NBR) bonded to a steel insert, on each side. Its lip presses against the inner ring.
- Much better protection against moisture, fine dust and fibres.
- More friction, so it runs a little warmer.
- Lower speed limit than a shielded bearing, because of the rubbing lip.
- Standard nitrile seals are made for roughly up to 100 °C in continuous use.
Which one should you use?
| Application | Usually |
|---|---|
| Electric motors in a clean, dry area | ZZ |
| High-speed spindles and power tools | ZZ |
| Pumps, washing and wet areas | 2RS |
| Dusty sites: cement, stone, flour, construction | 2RS |
| Textile machinery (lint and fibre) | 2RS |
| Agricultural and outdoor equipment | 2RS |
| Hot running, above about 100 °C | ZZ with high-temperature grease, or special high-temperature seals |
The simplest rule: replace like with like. If the original bearing was ZZ and it lasted well, fit ZZ again. If a ZZ bearing keeps failing with rust or grit inside, switching to 2RS is often the fix.
What about one of each?
A single Z or RS bearing has a shield or seal on one side only. These are used where the open side faces an oil bath or a sealed gearbox. Check which way round the old one was fitted before you remove it.
A middle option
Most makers also offer low-friction, non-contact seals: SKF 2RSL, NTN LLB and NSK VV. They protect better than a shield and run almost as freely. Ask us if you want to try one.
Not sure what your machine needs? Tell us the application, the speed and the environment, and we will suggest the right version.