Rolex GMT-Master II vs Tudor Black Bay GMT
Rolex GMT-Master II 126710GRNR-0003 vs Tudor Black Bay GMT 79830RB-0001, compared on the specs each brand publishes.
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The short answer
Two GMT watches from the same group, compared on published specs.
- Case size: the Tudor Black Bay GMT 79830RB-0001 is 1 mm larger (41 mm vs 40 mm).
- Water resistance: the Tudor Black Bay GMT 79830RB-0001 is 100 m more (200 m vs 100 m).
- Calibre: Rolex GMT-Master II 126710GRNR-0003 has 3285; Tudor Black Bay GMT 79830RB-0001 has MT5652.
- Certification: Rolex GMT-Master II 126710GRNR-0003 has COSC chronometer (Rolex Superlative Chronometer); Tudor Black Bay GMT 79830RB-0001 has COSC chronometer.
Side-by-side specs
| Spec | Rolex GMT-Master II 126710GRNR-0003 | Tudor Black Bay GMT 79830RB-0001 |
|---|---|---|
| Case diameter | 40 mm | 41 mm |
| Thickness | Not published by Rolex | 14.6 mm |
| Lug width | Not published by Rolex | 22 mm |
| Calibre | 3285 | MT5652 |
| Movement | Automatic | Automatic |
| Power reserve | 70 h | 70 h |
| Water resistance | 100 m | 200 m |
| Crystal | Sapphire | Sapphire |
| Case material | Stainless steel | Stainless steel |
| Ships on | Bracelet | Bracelet |
| US list price | $12,000 (US list) | Not stated |
| Dial | Black | Black |
| Certification | COSC chronometer (Rolex Superlative Chronometer) | COSC chronometer |
| GMT | Yes | Yes |
| Status | In production | In production |
| Suits wrists of about our sizing guide | 16.0–17.9 cm | 16.4–18.3 cm |
Specs summarised in our own words from the brand's product pages: 126710GRNR-0003 source (checked 3 Nov 2026) 79830RB-0001 source (checked 3 Nov 2026). "Not published" means the brand page we checked doesn't list it, so we leave it blank rather than guess.
Wrist fit
Lug-to-lug decides overhang more than diameter does. Enter your wrist to see how each one should wear.
- Rolex GMT-Master II 126710GRNR-0003 –
- Tudor Black Bay GMT 79830RB-0001 –
Same rule of thumb as Watch Finder: case diameter of about 23.5% of your wrist circumference (−2 mm to +2.5 mm), and lug-to-lug no longer than about 29% of it plus 1 mm. A guide, not a rule; flat or round wrists differ.
Strap fit
Rolex doesn't publish the lug width of the Rolex GMT-Master II 126710GRNR-0003, so measure it before buying a strap. The Tudor Black Bay GMT 79830RB-0001 has 22 mm lugs. Size charts: Rolex size chart · Tudor lug width chart.
Which should you buy?
It is the more compact case on paper (40 mm across). Our sizing guide puts it at about 16.0–17.9 cm.
It has the higher water-resistance rating: 200 m vs 100 m.
Prices and where to buy
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More: All Rolex GMT-Master II references · All Tudor Black Bay Gmt references.
Questions
Which is bigger, the Rolex GMT-Master II 126710GRNR-0003 or the Tudor Black Bay GMT 79830RB-0001?
Per the brands, the Rolex GMT-Master II 126710GRNR-0003 is 40 mm across and the Tudor Black Bay GMT 79830RB-0001 is 41 mm.
Which is more water-resistant?
Rolex GMT-Master II 126710GRNR-0003: 100 m. Tudor Black Bay GMT 79830RB-0001: 200 m.
Have you tested these watches?
No. This comparison uses brand-published specs and our own analysis of them, not hands-on testing.
Watch.co is independent and not affiliated with any brand. We haven't handled these watches for this page: everything here comes from brand-published specs and our own analysis. Brand names are used only to identify products.