Deep groove ball bearing · 63 series (medium)
6311 bearing
55 × 120 × 29 mm
The 6311 is a deep groove ball bearing with a 55 mm bore, 120 mm outside diameter and 29 mm width. Larger section and higher load capacity than the 62 series.
- Bore d
- 55 mm 2.1654 in
- Outside diameter D
- 120 mm 4.7244 in
- Width B
- 29 mm 1.1417 in
- Dimension series
- 03
- Load directions
- Radial and moderate axial in both directions
Designation explained
What 6311 means
Standard bearing numbers encode the type, the dimension series and the bore. Anything after the base number — seals, clearance, cage — is a suffix.
| Part | Meaning |
|---|---|
6 | Deep groove ball bearing |
3 | Diameter series 3 (medium), dimension series 03 |
11 | 11 → 55 mm bore (11 × 5) |
Variants
Common 6311 variants
Suffixes change the bearing without changing its boundary dimensions. The exact letters differ between manufacturers — always order by the full designation from the maker you choose.
| Suffix | Example | Meaning |
|---|---|---|
Z / ZZ (2Z) | 6311-ZZ | Metal shield on one / both sides; keeps out coarse dirt, low friction |
RS / 2RS | 6311-2RS | Rubber contact seal on one / both sides; better protection against dust and water |
C2 | 6311-C2 | Internal radial clearance smaller than normal |
CN (no suffix) | 6311 | Normal internal clearance |
C3 | 6311-C3 | Internal clearance greater than normal — common for electric motors and heated shafts |
C4 | 6311-C4 | Internal clearance greater than C3 |
| Manufacturer | Shields both sides | Contact seals both sides |
|---|---|---|
| SKF | 6311-2Z | 6311-2RS1 |
| FAG (Schaeffler) | 6311-2Z | 6311-2RSR |
| NSK | 6311-ZZ | 6311-DDU |
| NTN | 6311-ZZ | 6311-LLU |
| Koyo (JTEKT) | 6311-ZZ | 6311-2RS |
6311-2RS (sealed)
- Rubber contact seals on both sides
- Best protection against dust, water and grease loss
- Slightly more friction and a lower speed limit
- Choose for dirty, wet or outdoor use
6311-ZZ / 2Z (shielded)
- Metal shields on both sides, small gap to the inner ring
- Keeps out coarse dirt; not water-tight
- Lower friction, higher speeds
- Choose for clean, fast-running applications
Same envelope
Same 55 × 120 × 29 mm, different type
These bearings have exactly the same bore, outside diameter and width but are a different type. They fit the same housing and shaft, but carry loads differently — same size is not the same function.
Same bore
Other 55 mm bore bearings
Every standard bearing in this reference with a 55 mm bore, from light to heavy sections.
| Designation | Type | D | B / H |
|---|---|---|---|
| 6011 | Deep groove ball bearing | 90 mm | 18 mm |
| 6211 | Deep groove ball bearing | 100 mm | 21 mm |
| 6411 | Deep groove ball bearing | 140 mm | 33 mm |
| 61811 | Deep groove ball bearing | 72 mm | 9 mm |
| 61911 | Deep groove ball bearing | 80 mm | 13 mm |
| 16011 | Deep groove ball bearing | 90 mm | 11 mm |
| 1211 | Self-aligning ball bearing | 100 mm | 21 mm |
| 2211 | Self-aligning ball bearing | 100 mm | 25 mm |
| 2311 | Self-aligning ball bearing | 120 mm | 43 mm |
| 7211 | Angular contact ball bearing | 100 mm | 21 mm |
| NU211 | Cylindrical roller bearing | 100 mm | 21 mm |
| NU2211 | Cylindrical roller bearing | 100 mm | 25 mm |
| NU2311 | Cylindrical roller bearing | 120 mm | 43 mm |
| 22211 | Spherical roller bearing | 100 mm | 25 mm |
| 22311 | Spherical roller bearing | 120 mm | 43 mm |
| 30211 | Tapered roller bearing | 100 mm | 22.75 mm |
| 30311 | Tapered roller bearing | 120 mm | 31.5 mm |
| 32011X | Tapered roller bearing | 90 mm | 23 mm |
| 32211 | Tapered roller bearing | 100 mm | 26.75 mm |
| 32311 | Tapered roller bearing | 120 mm | 45.5 mm |
| 51111 | Thrust ball bearing | 78 mm | 16 mm |
| 51211 | Thrust ball bearing | 90 mm | 25 mm |
| 51311 | Thrust ball bearing | 105 mm | 35 mm |
| UCP211 | Pillow block bearing unit | — | — |
Where to buy
Find 6311 at sellers
Search results on independent sellers. We are not affiliated with them, do not earn from these links and do not see their prices or stock. Results mix brands and variants — check the full designation before you order.
About these dimensions. Boundary dimensions follow ISO 15 (radial bearings — boundary dimensions, general plan), dimension series 03, and are the same for every manufacturer of a standard 6311. Chamfers, load ratings, speed limits and weight depend on the manufacturer and design and are not shown — use the maker's datasheet for engineering decisions. Last checked 9 October 2026. Spotted an error? Tell us.
Learn more
What size is a 6311 bearing?
A 6311 is a deep groove ball bearing with a 55 mm bore, 120 mm outside diameter and 29 mm width (55 × 120 × 29 mm). These boundary dimensions follow the ISO dimension plan, so they are the same across manufacturers.
What does 6311-2RS or 6311-ZZ mean?
Same size, different closures: 2RS has rubber contact seals on both sides, ZZ (2Z) has metal shields on both sides. Manufacturers use different letters for the same idea — for example NSK DDU or NTN LLU for contact seals.
Can I replace 6311 with another bearing of the same size?
Other bearing types can share the same 55 × 120 × 29 mm envelope, but a different type has different load directions, speed limits and mounting needs. Same dimensions alone do not make two bearings interchangeable.
Where are the load ratings and speed limits?
They depend on the manufacturer and internal design, so we do not list a single value. Check the datasheet for the exact full designation you intend to use.
Need 6311 data for a whole catalog?
We can help with that.
Normalized specifications, variants and supplier listings for every bearing you sell, with the source behind each value.