Omega
Omega Seamaster Planet Ocean 43.5 Strap Size — 21mm Lug Width
The Omega Seamaster Planet Ocean 43.5 has a 21mm lug width, so it takes a 21mm watch strap.
Lug width21mm
| Lug width | 21 mm |
|---|---|
| Case size | 43.5 mm |
| Lug-to-lug | 49 mm |
| Thickness | 16.1 mm |
| Spring bar Ø (typical) | Not confirmed |
| End type | Straight |
Which reference do you have?
Similar-looking models can take different straps. Your reference number is on the case back or your papers.
| Model | Case | Strap |
|---|---|---|
| Planet Ocean 600M 43.5mm | 43.5mm | 21mm |
| Seamaster Diver 300M | 42mm | 20mm |
Strap styles that fit
- NATO / Zulu21mm fits if the strap's thickness clears the case under the bars.
- PerlonWoven pass-through, 21mm.
- 2-piece leatherStraight ends fit flush.
- Rubber / siliconeDivers & sports fit well.
- Milanese / meshStraight-end 21mm mesh fits.
- Metal braceletNeeds 21mm end-links shaped for this case.
▲ 21mm — an uncommon size.
Fit & sizing notes for the Seamaster Planet Ocean 43.5
- Width: buy 21mm straps. Tapered straps listed as 21/19mm or 21/17mm fit too; only the first number has to match. See strap sizes explained.
- Spring bars: 21mm long. We haven't confirmed the diameter for this model, so measure the old bar before buying replacements (spring bar sizes).
- Odd size: 21mm straps are harder to find; a 20mm strap fits with a small gap, but never go wider. Odd lug width options.
- Wrist fit: at 49mm lug-to-lug it should sit within the top of wrists from about 16.3cm up (rule of thumb: lug-to-lug under ~30% of wrist size). That's longer than 81% of the watches in our index. See what size watch suits your wrist.
- Strap thickness: at 16.1mm thick it's a chunky case: thicker padded leather, rubber/FKM or a heavier NATO balance it visually; very thin straps can look undersized.
Sources & corrections
Lug width checked against: Bernard Watch: Planet Ocean 600M; Market Cross: Planet Ocean 43.5mm. Last checked 24 October 2026.
Spec wrong for your watch? Send us a correction with your reference number.
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Omega Seamaster Planet Ocean 43.5 — strap questions
What size strap does the Seamaster Planet Ocean 43.5 take?
The Omega Seamaster Planet Ocean 43.5 has a 21mm lug width, so you need a 21mm watch strap.
Will any 21mm strap fit the Seamaster Planet Ocean 43.5?
Most will. Width is the main thing to match, but also check that the strap's spring-bar holes suit the bars, and that the strap is thin enough to clear the case between the lugs. A metal bracelet needs 21mm end-links made for this model.
What spring bar size does the Seamaster Planet Ocean 43.5 use?
21mm long. We haven't confirmed the diameter for the Seamaster Planet Ocean 43.5, so measure the original bar with calipers before buying replacements.
Is the Seamaster Planet Ocean 43.5 good for strap swapping?
Yes. With standard 21mm spring-bar lugs, NATO, leather, rubber and mesh straps can all be fitted with a spring-bar tool.