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What Do Z, ZZ, 2RS, DU, LLU, and RZ Mean on Bearings?
What Are Bearing Suffixes?
Bearing suffixes are letters or numbers added after the basic bearing model number. They describe special design features, such as:
- Seal or shield type
- Internal clearance
- Cage material
- Precision grade
- Lubrication
- Heat treatment
- Special structure, etc.
For example:
6205ZZ means a 6205 bearing with metal shields on both sides.
6205-2RS means a 6205 bearing with rubber seals on both sides.
Among all suffixes, Z, ZZ, RS, 2RS, DU, LLU, and RZ are commonly related to sealing and shielding.
Bearing Suffix Meanings: Comparison Chart:
| SKF | FAG | NSK | NTN | KOYO | NACHI | |
| Metal shield on one side | Z | ZR | Z, ZS | Z | Z | Z |
| Metal shields on both sides | 2Z | 2ZR | ZZ | ZZ | ZZ | ZZ |
| Single non-contact rubber seal | RZ | RSD | LB | RU | RU | NK |
| Double non-contact rubber seals | 2RZ | 2RSD | LLB | 2RU | 2RU | 2NK |
| Single contact rubber seal | RS1, RSH | RSR | DU | LU | RS | NS |
| Double contact rubber seals | 2RS1, 2RSH | 2RSR | DDU | LLU | 2RS | 2NS |
| Outer ring with retaining groove | N | N | N | N | N | N |
| Outer ring with retaining ring and groove | NR | NR | NR | NR | NR | NR |
ZZ vs 2RS Bearings: What Is the Difference?
| Feature | ZZ Bearing | 2RS Bearing |
|---|---|---|
| Seal type | Metal shields | Rubber seals |
| Protection | Basic dust protection | Better dust and moisture protection |
| Friction | Lower | Higher |
| Speed | Higher speed | Lower speed than ZZ |
| Grease retention | Good | Better |
| Best for | Clean, high-speed applications | Dusty, wet, or dirty environments |
In simple terms, choose ZZ bearings when speed and low friction are more important. Choose 2RS bearings when sealing, grease retention, and contamination protection are more important.
Contact Seal vs Non-Contact Seal Bearings:
A contact seal touches the inner ring of the bearing. It provides stronger protection against dust, moisture, and grease leakage, but it also creates more friction.
A non-contact seal does not directly touch the inner ring. It creates less friction and is better for higher-speed applications, but the sealing performance is usually not as strong as a contact seal.
| Seal Type | Advantages | Disadvantages | Common Codes |
|---|---|---|---|
| Contact seal | Better sealing, better grease retention | Higher friction, lower speed | 2RS, DU, LLU |
| Non-contact seal | Lower friction, higher speed | Weaker sealing than contact seals | RZ, 2RZ, LLB, RU |
Conclusion:
Understanding bearing suffix meanings makes it easier to select a bearing that matches the actual working environment. Suffixes such as Z, ZZ, 2RS, DU, LLU, and RZ indicate the type of protection used on the bearing, including metal shields, contact rubber seals, or non-contact rubber seals.
