2RS vs ZZ: bearing seals and shields
ZZ is a metal shield, 2RS a rubber seal. Differences in dust, water, speed and friction, open bearings, and seal codes by brand.
Last updated: 6 November 2026
The letters at the end of a bearing code give the seal type. A single letter means one side, a double letter means both sides.
| Code | Type | Meaning |
|---|---|---|
| No letter | Open | No seal, lubricated from outside |
| Z | One metal shield | Closed on one side |
| ZZ or 2Z | Two metal shields | Closed on both sides |
| RS | One rubber seal | Sealed on one side |
| 2RS | Two rubber seals | Sealed on both sides |
Metal shield or rubber seal?
| Property | ZZ (metal shield) | 2RS (rubber seal) |
|---|---|---|
| Friction and heat | Low | Higher, the seal touches the ring |
| High speed | Better suited | Lower speed limit |
| Fine dust | Limited protection | Better protection |
| Water and moisture | No protection | Protects against splashes |
| Lubrication | Greased at the factory | Greased at the factory |
In short: 2RS suits dusty and damp conditions, ZZ suits clean conditions and high speeds. Where a bearing runs in water, 2RS alone is not enough and extra sealing is needed. Standard rubber seals (NBR) are good to about 100 °C; in hotter conditions consider metal shields or special seals.
When to use an open bearing
Open bearings are used in oil baths or where a grease pump lubricates from outside. Sealed bearings are generally not regreased, so they keep their grease, and are replaced at the end of their life.
Codes by brand
The same seal type is written differently by each brand. For 6205:
| Brand | Two metal shields | Two rubber seals |
|---|---|---|
| SKF | 6205-2Z | 6205-2RSH |
| FAG | 6205-2Z | 6205-2RSR |
| NSK | 6205ZZ | 6205DDU |
| NTN | 6205ZZ | 6205LLU |
| KOYO | 6205ZZ | 6205-2RS |
To see which option is in stock, enter the code in the Bearing finder. For the rest of the code, see how to read a bearing code.