At a glance
Z / one shield
One face has a non-contact shield and the opposite face is usually open.
Choose where the housing provides protection on one side and lubricant access is intentional.
ZZ / 2Z
Both faces have metal shields, usually around a factory grease fill.
Choose for retained grease in a protected, relatively clean environment.
Key differences
Typical design distinctions. The complete designation and current product specification take precedence.
Swipe the table horizontally to see both options →
| What to compare | Z / one shield | ZZ / 2Z |
|---|---|---|
| Shield count | One | Two |
| Lubricant access | Open side remains accessible | Two shields restrict access |
| Orientation | Shield direction matters | Usually the same closure on each face |
| Water exclusion | Not a liquid seal | Two shields still do not make a liquid seal |
| Speed | Verify specific lubricant and cage | Verify specific lubricant and cage |
| Cross-brand notation | Z often means one shield | ZZ and 2Z often mean two shields |
Before you choose
- A shield's narrow gap is not proof of a contact seal.
- Double-shielded does not mean maintenance-free under every temperature or service duration.
- Special product families can use a different suffix convention.
Check the actual model
Search a full designation, inspect its technical data, then compare candidate records. Similar names or dimensions do not guarantee interchangeability.
Filters show recorded catalogue attributes. Open each candidate to confirm its exact specification.
A few things worth clarifying
Are ZZ and 2Z interchangeable codes?
Often they describe two shields, but cross-brand substitution requires the full dimensional and performance checks.
Does a second shield make the bearing waterproof?
No. The running gaps remain paths for liquid under unsuitable exposure.
Reference basis & limits
- SKF — Bearing maintenance handbook: designation suffixes
- NSK — Single-row deep groove ball bearings: features and closure designations
Independent explanatory content; not a manufacturer endorsement or approval of a replacement. Verify current product data, fits, lubrication and operating conditions before applying a comparison.