Choosing between open, shielded, and sealed bearings depends on your lubrication and contamination requirements.
Open bearings
- No closures. Rolling elements are exposed.
- Must be lubricated by the machine’s oil system or manually greased.
- Best for: gearboxes with oil-bath lubrication, high-speed spindles with oil-mist systems.
- Not suitable for dirty environments unless the housing has its own seals.
Shielded (ZZ or Z)
- Metal shields, non-contact, pressed into the outer ring.
- Retain factory grease. Provide moderate dust protection.
- Lower friction than seals. Higher speed capability.
- Best for: electric motors, fans, clean indoor environments.
Sealed (2RS or 2RSH)
- Rubber seals with lip contact on the inner ring.
- Excellent grease retention and contamination exclusion.
- Slightly higher friction than shields.
- Best for: conveyors, pumps, agricultural machinery, outdoor equipment.
Quick guide
| Application | Recommendation |
|---|---|
| Electric motor (standard) | ZZ or 2RS (both common) |
| Conveyor (dusty) | 2RS |
| Food processing (washdown) | 2RS, stainless steel |
| Gearbox (oil bath) | Open |
| High-speed spindle | Open or ZZ |
| Agricultural PTO | 2RS |
When replacing a bearing, match the original closure type unless you have a reason to change. Switching from open to sealed improves reliability in most MRO environments.