Deep groove ball bearing · 63 series (medium)
6321 bearing
105 × 225 × 49 mm
The 6321 is a deep groove ball bearing with a 105 mm bore, 225 mm outside diameter and 49 mm width. Larger section and higher load capacity than the 62 series.
- Bore d
- 105 mm 4.1339 in
- Outside diameter D
- 225 mm 8.8583 in
- Width B
- 49 mm 1.9291 in
- Dimension series
- 03
- Load directions
- Radial and moderate axial in both directions
Designation explained
What 6321 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 |
21 | 21 → 105 mm bore (21 × 5) |
Variants
Common 6321 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) | 6321-ZZ | Metal shield on one / both sides; keeps out coarse dirt, low friction |
RS / 2RS | 6321-2RS | Rubber contact seal on one / both sides; better protection against dust and water |
C2 | 6321-C2 | Internal radial clearance smaller than normal |
CN (no suffix) | 6321 | Normal internal clearance |
C3 | 6321-C3 | Internal clearance greater than normal — common for electric motors and heated shafts |
C4 | 6321-C4 | Internal clearance greater than C3 |
| Manufacturer | Shields both sides | Contact seals both sides |
|---|---|---|
| SKF | 6321-2Z | 6321-2RS1 |
| FAG (Schaeffler) | 6321-2Z | 6321-2RSR |
| NSK | 6321-ZZ | 6321-DDU |
| NTN | 6321-ZZ | 6321-LLU |
| Koyo (JTEKT) | 6321-ZZ | 6321-2RS |
6321-2RS (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
6321-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 105 × 225 × 49 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 105 mm bore bearings
Every standard bearing in this reference with a 105 mm bore, from light to heavy sections.
Where to buy
Find 6321 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 6321. 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 6321 bearing?
A 6321 is a deep groove ball bearing with a 105 mm bore, 225 mm outside diameter and 49 mm width (105 × 225 × 49 mm). These boundary dimensions follow the ISO dimension plan, so they are the same across manufacturers.
What does 6321-2RS or 6321-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 6321 with another bearing of the same size?
Other bearing types can share the same 105 × 225 × 49 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 6321 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.