The Cartier Ballon Bleu WGBB0017 is the full rose gold 42 on leather — 18K rose gold case, silver guilloché dial, blued sword hands, date at 3, brown alligator strap with an 18K rose gold folding buckle. If your papers carry this number, you own the biggest expanse of precious metal Cartier puts on a wrist, and you own something else too: the heaviest Ballon Bleu in the lineup.
That weight is exactly where the strap conversation starts on this reference — because on a solid gold 42, the strap isn't decoration. It's load-bearing. Correct size first.
Cartier Ballon Bleu WGBB0017 Strap Size and Fit
The essentials:
- Reference: WGBB0017, Ballon Bleu de Cartier, 42 mm, 18K rose gold, automatic
- Correct strap size: 20 mm
On the product page, select the 20 mm option. The Ballon Bleu's convex case and short curved lugs need a strap shaped for the model — flat generic straps gape against the rounded case — and every Helvetus Ballon Bleu strap ships complete with its own buckle. The watch takes straps on standard spring bars; any watchmaker swaps one in minutes.
Two notes for this reference specifically:
The reference numbers. Cartier has used more than one number for the rose gold 42 on leather over the years — same 42 mm case, so every version takes 20 mm. Whichever number is on your paperwork, the size is identical.
The ladder. Size by case, not photos: 28 mm → 14 mm, 33 mm → 16 mm, 36 mm → 18 mm, 42 mm → 20 mm. At 42 mm, yours is the largest — and the only men's-size gold in the family.
Solid Gold Has Consequences
Everything about the WGBB0017 is the Ballon Bleu formula at maximum: the pebble-round case in warm 18K rose gold, the fluted crown holding a blue sapphire cabochon, silver guilloché dial with Roman numerals and an inner minute track, blued sword hands, a date at 3 o'clock, an automatic movement inside, 13 mm thick, 30 meters water resistance.
And here's the physics nobody mentions in the boutique: gold is far denser than steel. A 42 mm case in solid rose gold carries real weight — and weight is hard on straps. Leather under a heavy head stretches at the buckle holes, creases faster at the flex points, and softens sooner than the same strap under a steel watch. Which changes two things: your factory alligator will wear out sooner than you expect, and a fresh, firm strap isn't a style choice on this watch — it's what makes a heavy gold case sit still and wear comfortably instead of rolling on the wrist. These are the most popular strap choices among gold Ballon Bleu owners:
1. Black Leather – The Workhorse Under the Weight
A black leather strap for the Cartier Ballon Bleu is the strap this watch should spend its weekdays on: firm, fresh, and matte — it carries the gold securely, spares the factory alligator the daily stretching, and gives the rose gold the dark contrast that makes it read richest. Rotate it with the factory strap and both last dramatically longer — arithmetic that matters when one of the two came from Cartier in gold-buckled alligator.
2. Black Crocodile – The Evening Successor
When the factory alligator does crease and soften — under this weight, a when, not an if — a black crocodile strap restores the exotic-leather register the watch was sold in, in the color that flatters gold most. Formal, substantial, and the natural choice for the occasions a solid gold 42 was bought for.
3. Blue Leather – Cool Against the Warmth
The sapphire cabochon in the crown and the blued sword hands are the only cool notes Cartier put on this watch — a deliberate counterpoint to all that warm gold. A blue leather strap extends that counterpoint down the wrist: navy against rose gold is one of the most confident pairings in modern watch dressing, and it keeps a big gold watch feeling composed rather than loud.
4. Blue Crocodile – The Statement, Properly Made
Both ideas at once: the watch's own cool accent in occasion-grade texture. A blue crocodile strap is the most distinctive way to wear the rose gold 42 — unmistakably deliberate, and still disciplined enough to let the gold and the guilloché lead.
Every compatible option in 20 mm is in the full Cartier Ballon Bleu strap collection.
Guard the Gold Buckle
One more thing worth protecting: your factory strap carries an 18K rose gold folding buckle — likely the most valuable buckle you'll ever own. Keep it safely with the original alligator as a complete set; on a gold reference, complete factory sets hold their value best when the watch is ever appraised or sold.
Final Thoughts
The WGBB0017 asks its strap to do real work: carry solid gold comfortably, wear out gracefully, and step aside for the stones-and-guilloché show above it. Helvetus is one of the leading names in the aftermarket strap world, and our Ballon Bleu straps are shaped for the curved 42 mm case — an exact 20 mm fit, buckle included. Rubber straps across our range carry a lifetime warranty, shipping is free worldwide with no import costs, and more than 50,000 watch owners already trust us with their straps.
Cartier gave this watch its weight in gold. Give it a strap built to carry it.
