308-ZZ bearing: complete specifications & equivalents
The 308-ZZ is a ISO 15 radial bearing sized 40 x 90 x 23 mm (bore x OD x width) with ZZ sealing. Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 23 mm |
| Material | GCr15 |
| Seal / shield | ZZ |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 45.7 kN |
| Basic static load rating C0 | 36 kN |
| Fatigue load limit Pu | 1.53 kN |
| Reference speed (thermal) | 14000 rpm |
| Limiting speed (mechanical) | 6800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 640 g |
| Manufacturer designation | 308-2Z |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & 300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 0.906 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 300-series | 25 mm |
| Largest outer diameter in 300-series | 190 mm |
| Width range across 300-series | 17–43 mm |
| Bore position in 300-series (smallest first) | 4 of 14 |
| Bore above smallest 300-series size | 15 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 308 | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×23 mm envelope and equivalent catalogue ratings; 308 is the open arrangement execution of this size — boundary dimensions interchangeable, only the seal/shield/cage execution differs. |
| 6308 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6308 shares the 40×90×23 mm envelope but catalogue C/C0 differ (45.7/36 kN vs 42.3/24 kN) — envelope match, not a load-rating equivalent. |
| 6308-ZZ | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6308-2Z shares the 40×90×23 mm envelope but catalogue C/C0 differ (45.7/36 kN vs 42.3/24 kN) — envelope match, not a load-rating equivalent. |
| 6308-2RS | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6308-2RSH shares the 40×90×23 mm envelope but catalogue C/C0 differ (45.7/36 kN vs 42.3/24 kN) — envelope match, not a load-rating equivalent. |
| 6308-RSR | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 6308-2RZ shares the 40×90×23 mm envelope but catalogue C/C0 differ (45.7/36 kN vs 42.3/24 kN) — envelope match, not a load-rating equivalent. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 308-ZZ model number is decoded
308-2Z is a filling-slot (notched-ring) deep-groove bearing in the legacy 300-series: the last two digits encode the bore: 308 carries code 08 = 40 mm (code × 5). The rings carry loading slots that allow extra balls during assembly, which is what gives the 40×90×23 mm envelope its C 45.7 kN and C0 36 kN ratings (Pu 1.53 kN). SKF spells the double shield 308-2Z (suffix 2Z); the shields are non-contact, retain grease and block coarse debris but are not liquid-tight. Limiting speed 6800 r/min, mass 640 g. These bearings are built for high purely-radial loads at moderate speeds.
Typical equipment & failure modes
Common applications
- construction equipment drives
- hoists and winch gear trains
- eccentric and vibratory conveyors
- legacy machinery repairs
Known failure patterns
- spalling of the filling-slot edge when balls are hammered through the slot under heavy thrust loading
- dirt entering through the open slot area when external sealing is neglected
- fretting corrosion on a creeping shaft or housing seat
- cage damage from running beyond the limiting speed
Selection pitfalls — read before you substitute
- The slots sit at one angular position: on 308-ZZ, never pass the full radial load across the slot zone during mounting or the ring lip can crack.
- 308 uses the legacy SKF 200/300 numbering (light/heavy filling-slot series), not the modern 6200/6300 spelling; quote 308-2Z exactly when ordering replacements.
- Filling-slot bearings take heavy purely-radial load at moderate speed but little thrust; the 45.7/36 kN ratings assume radial loading — use deep-groove 6xxx where axial load matters.
- Shields on 308-ZZ retain grease but do not seal against water; for wet farm duty add external lip seals rather than trusting the shield.
- The slots sit at one angular position: on 308-ZZ, never pass the full radial load across the slot zone during mounting or the ring lip can crack.
- Clearance suffixes follow the seal code in the designation stack (e.g. 308-2Z/C3 in SKF spelling); no suffix means normal CN internal clearance.
Frequently asked questions
What are the dimensions of 308-ZZ?
Filling-slot bearing 308-2Z measures 40×90×23 mm (1.575×3.543×0.906 in), about 640 g.
What does the designation 308 mean?
It is the legacy 200/300 filling-slot numbering: series 300 and bore code 08 = 40 mm. Filling-slot bearings predate the 6xxx deep-groove spelling.
Why use an old 300-series bearing instead of a 62xx?
For slow, heavy, purely-radial duty the extra balls give more capacity in the same bore, and the separable rings simplify assembly in blind housings; at high speed modern designs run better.
What fails on 308-ZZ?
Slot-edge chipping under thrust or shock, dirt ingress in the open design and cage wear past the 6800 r/min limiting speed are the typical failure modes.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-27. Read our editorial & correction policy.