12 min read · 26 Jun 2026 · SLS Engineering Team
Bearing Nomenclature Guide — Complete Suffix & Prefix Chart (SKF, FAG, NSK, NTN, KOYO)
Decode bearing part numbers across SKF, FAG, NSK, NTN and KOYO — what ZZ, 2RS, C3, P5, K, NR, W33, CC, RS1, DDU, VV and other suffixes actually mean, with a quick reference chart.
Choosing the correct bearing is not just about dimensions. Modern rolling bearings carry suffixes, prefixes and designation codes that describe sealing, internal clearance, precision class, cage material, lubrication, mounting arrangement, insulation and heat treatment.
Whether you're searching for the meaning of ZZ, 2RS, C3, P5, K, NR, W33, CC, or specialty bearings like INSOCOAT insulated bearings, this guide explains the most commonly used bearing nomenclature across SKF, FAG, NSK, NTN, KOYO, NACHI and other leading manufacturers.
At SLS Bearings India we stock all major brands — if you're unsure what a code on your old bearing means, [send us the number](/rfq) and we'll cross-reference it for you.
What is bearing nomenclature?
Bearing nomenclature is the standardised identification system manufacturers use to describe a bearing's design and features.
Example: SKF 6205-2Z/C3
| Code | Meaning |
|---|---|
| 6 | Deep groove ball bearing |
| 2 | Diameter series |
| 05 | Bore code (25 mm) |
| 2Z | Metal shields on both sides |
| C3 | Greater than normal internal clearance |
All manufacturers follow ISO 15 for basic designation, but suffixes differ slightly between brands.
Shield and seal suffixes
Z — single metal shield
- Protects against dust on one side
- Non-contact, low friction, high-speed friendly
- Grease retained inside
Used in: electric motors, fans, pumps, gearboxes.
ZZ — metal shields on both sides
Most manufacturers use ZZ. Examples: 6204ZZ, 6308ZZ, 6210ZZ.
2Z — SKF designation for ZZ
SKF uses 2Z instead of ZZ. Example: SKF 6205-2Z.
> ZZ and 2Z mean exactly the same thing — two metal shields, non-contact, factory-greased, maintenance-free. The difference is only manufacturer terminology.
RS — single rubber seal
- Better dust and water resistance than a shield
- Slightly higher friction
Used in: agricultural machinery, textile machinery, conveyors.
2RS — rubber seals on both sides
- Excellent contamination protection
- Better grease retention
- Longer life in dirty environments
Used in: automotive, construction equipment, food machinery, mining.
RS1 / 2RS1 (SKF)
SKF designation for a reinforced NBR contact seal (single or double). Equivalent to other brands' RS / 2RS. Example: SKF 6205-2RS1.
RSH (SKF) — heavy-duty contact seal
Better contamination and water resistance, longer grease life.
RSL (SKF) — low-friction contact seal
For higher speeds and lower running temperature with good sealing.
RZ / 2RZ — low-friction non-contact rubber seal
Less friction than RS, better protection than Z. Ideal for high-speed electric motors.
DU / DDU (NSK)
- DU = single contact rubber seal (≈ RS)
- DDU = both sides sealed (≈ 2RS)
VV (NSK)
Two non-contact rubber seals — low torque, high speed, dust protection.
LLU / LLB (NTN)
- LLU = double contact rubber seal
- LLB = double non-contact rubber seal
Quick comparison
| Code | Meaning |
|---|---|
| Z | One metal shield |
| ZZ | Two metal shields |
| 2Z | SKF designation for ZZ |
| RS | One rubber seal |
| 2RS | Two rubber seals |
| RS1 / 2RS1 | SKF reinforced rubber seal |
| RSH | SKF heavy-duty contact seal |
| RSL | SKF low-friction contact seal |
| RZ / 2RZ | Non-contact rubber seal |
| DU / DDU | NSK single / double rubber seal |
| VV | NSK non-contact seals |
| LLU / LLB | NTN contact / non-contact seal |
Internal clearance suffixes
Internal clearance is the play between rolling elements and raceways. It changes with operating temperature and shaft fits.
| Code | Clearance |
|---|---|
| C1 | Less than C2 |
| C2 | Less than normal |
| CN | Normal (often omitted) |
| C3 | Greater than normal — most common for motors and gearboxes |
| C4 | Greater than C3 — high temperature applications |
| C5 | Greater than C4 — extreme heat / heavy interference fits |
Rule of thumb: if the bearing runs hot or has a tight shaft fit, step up to C3 or C4.
Precision class (tolerance) suffixes
Defined by ISO 492 and ABEC standards.
| ISO | ABEC | Use case |
|---|---|---|
| Normal (P0) | ABEC 1 | General industry |
| P6 | ABEC 3 | Light machine tools |
| P5 | ABEC 5 | Machine-tool spindles, electric motors |
| P4 | ABEC 7 | High-speed spindles |
| P2 | ABEC 9 | Ultra-precision spindles |
Cage material suffixes
| Code | Cage material |
|---|---|
| J | Pressed steel (standard for many ball bearings) |
| Y | Pressed brass |
| M / MA / MB | Machined brass |
| TN / TNH / TVH | Polyamide (PA66) |
| F | Machined steel |
| CA / CC / E | Internal design / machined cage variants (spherical rollers) |
For spherical roller bearings, CC and CA designate different internal designs — common on 22220, 22222, 22228 and similar.
Bore and mounting suffixes
| Code | Meaning |
|---|---|
| K | Tapered bore 1:12 (mounts on adapter sleeve) |
| K30 | Tapered bore 1:30 (large spherical rollers) |
| W33 | Annular groove and 3 lubrication holes in outer ring |
| N | Snap ring groove on outer ring |
| NR | Snap ring groove + snap ring supplied |
| 2LS | Contact seals on both sides (spherical rollers) |
Example: 22220 EK/C3 W33 = spherical roller, E-design, tapered bore, C3 clearance, lubrication groove.
Lubrication and special suffixes
| Code | Meaning |
|---|---|
| /HT | High-temperature grease |
| /LT | Low-temperature grease |
| /MT47 | SKF standard lithium grease |
| /GJN | SKF high-temperature grease |
| /VL0241 | SKF INSOCOAT — electrically insulated (coated outer ring) |
| /VL2071 | SKF INSOCOAT — coated inner ring |
| /HC5 | Hybrid bearing with ceramic (Si3N4) rolling elements |
INSOCOAT bearings prevent stray current passage in variable-frequency-drive motors — critical for wind turbines, traction motors and large VFD-driven plant motors.
Heat-treatment / stabilisation suffixes
| Code | Stable up to |
|---|---|
| S0 | 150 °C |
| S1 | 200 °C |
| S2 | 250 °C |
| S3 | 300 °C |
| S4 | 350 °C |
Use S1 or higher in cement plant fans, furnace conveyors and steel-mill applications.
Brand cheat-sheet
Same feature, different suffix:
| Feature | SKF | FAG | NSK | NTN | KOYO / NACHI |
|---|---|---|---|---|---|
| Two metal shields | 2Z | 2Z / 2ZR | ZZ | ZZ | ZZ |
| Two rubber contact seals | 2RS1 | 2RSR | DDU | LLU | 2RS |
| Two non-contact rubber seals | 2RZ | 2RSR.L038 | VV | LLB | 2NSE |
| C3 clearance | C3 | C3 | C3 | C3 | C3 |
| Polyamide cage | TN9 | TVH | T | T2 | TN |
Which sealing should you choose?
| Environment | Recommended |
|---|---|
| Clean, high speed | ZZ / 2Z |
| Dusty | 2RS |
| Wet | 2RS |
| Electric motor | 2Z or RZ |
| Agriculture | 2RS |
| Automotive | 2RS |
| Food machinery | Stainless + 2RS |
| High RPM spindle | ZZ / 2Z (or open with oil) |
A note on brand differences
ISO 15 defines basic bearing dimensions and most designation conventions, but suffixes for cages, greases and internal designs are manufacturer-specific. Always verify against the manufacturer's catalogue before ordering specialty bearings.
Need help decoding a part number?
Send us the number stamped on your bearing and we'll identify it, suggest a brand-by-brand cross-reference, and quote the same working day.
- Browse [bearing types](/bearings) for series, sizes and applications
- See the [brands we stock](/brands) — SKF, FAG, NTN, NSK, KOYO, Timken
- [Request a quote](/rfq) with your part number and we'll get back to you
Understanding bearing nomenclature is the difference between ordering the right bearing and shutting your line down twice. Bookmark this guide — and when in doubt, ask.
Talk to SLS Bearings India
Have a real bearing problem we should write about — or one we should solve? Reach our team.