Most Ballon Bleu dials are guilloché — a fixed pattern that holds still while the light moves over it. The WJBB0034 is not. Its dial is sunray-brushed, which means the finish throws a band of light that sweeps across the face as your wrist turns.
Now add the bezel: 18K rose gold set with 54 brilliant-cut diamonds, 0.79 carats, each one firing in a different direction as you move.
That gives this watch two independent light sources, both of them in motion, before you have chosen anything. Which makes the strap's job unusually clear — it needs to be the still part.
The rest of the specification: 36 mm rose gold case, 12.1 mm thick, automatic movement, silvered sunray dial with black Roman numerals and blued-steel sword hands, the fluted crown with its sapphire cabochon, and a burgundy alligator strap with an 18K rose gold ardillon buckle.
Lug Width: the WJBB0034 takes an 18 mm strap
On the product page, select the 18 mm option.
The 36 mm Ballon Bleu case uses an 18 mm strap, and the gold version shares its case footprint with the steel one. The figure is consistent across independent strap-size charts for the 36, the original Cartier strap dimensions, and the 18 mm size we stock for the model.
| Case | Strap size |
|---|---|
| 42 mm | 20 mm |
| 36 mm (WJBB0034) | 18 mm |
| 33 mm | 16 mm |
| 28 mm | 14 mm |
Three things to get right:
- Standard spring bars. This is a strap watch with a conventional attachment — no proprietary fitting to work around. A spring bar tool or our installation tool is enough.
- Tape the lugs. Rose gold is soft and there are 54 stones set into the bezel above them. Masking tape costs nothing; a slip near a diamond setting does not.
- Rose gold buckle. Our Ballon Bleu straps are ordered with a buckle finish, and the factory buckle here is an 18K rose gold ardillon. Rose gold is the match — yellow gold sits close enough to look like a mistake rather than a mix, and silver reads as a different watch entirely.
Why a busy watch wants a quiet strap
There is a version of this article that tells you to have fun with colour. It would be wrong for this reference, and the reason is worth understanding.
Texture and sparkle both compete for the same attention. A sunray dial is already changing as you move; a diamond bezel is already scattering light in every direction. Put something equally active underneath — a bright colour, a glossy finish, a heavy pattern — and the eye has three things asking for it at once. Nothing wins, and the watch looks busier rather than richer.
The strap that works is the one that gives all of that motion something steady to sit against. That is also, almost certainly, why Cartier chose a deep burgundy alligator rather than a bright one: dark enough to frame the stones, quiet enough to stay out of the way, and textured in a way that reads as expensive without shouting.
So the question here is not which colour. It is dark or cool — and how much texture you want at the boundary between the strap and the case.
The four best straps for the WJBB0034
1. Black crocodile — the frame this watch is asking for
Black Crocodile Strap for Cartier Ballon Bleu
The nearest thing in our range to what Cartier fits, and the best answer to the brief. Black is the highest contrast available, which is exactly what makes 54 stones catch light, and rose gold has never needed help looking warm — it needs something dark next to it to look deliberate. Crocodile matters as much as the colour: on a diamond-set bezel, an exotic skin answers in the same register, where a plain band under a set case can look like a mismatch of ambition. If you buy one strap for this watch, buy this one.
2. Blue crocodile — the cool counterweight
Blue Crocodile Strap for Cartier Ballon Bleu
Blue is already on the watch — the cabochon in the crown, the blued steel of the hands — and blue against rose gold has become one of the most reliable pairings in modern jewellery. It cools a very warm watch without introducing a colour that argues with the gold, and in crocodile it keeps the formality the diamonds ask for. The most contemporary way to wear the reference, and the one that photographs least like everything else.
3. Black leather — the everyday version
Black Leather Strap for Cartier Ballon Bleu
Same logic as the crocodile, none of the preciousness. Smooth black is the calmest surface you can put under a sunray dial and a diamond bezel, and it is the strap you will not think twice about wearing — which matters more than it sounds on a watch at this level. Owning one strap you are relaxed about is worth more than owning two you are careful with.
4. Blue leather — cool, and easy
Blue Leather Strap for Cartier Ballon Bleu
The everyday member of the blue family: the same cooling effect, in a material that suits a Tuesday. It is the least formal of the four and the most wearable in daylight, when a sunray dial is at its most alive and the watch needs the least help from anything else.
Every colour and size is in the Cartier Ballon Bleu strap collection.
Cartier makes the same idea in white gold as the WE900651 — a diamond bezel on a colder metal, and a very different strap decision. It takes the same 18 mm.
Fit, in one line
Order 18 mm with the rose gold buckle, tape the lugs, and fit it with standard spring bars.
More Cartier strap guides
The strap is the part that ages
There is no bracelet for this reference. The alligator it arrived on is the only wearing component the watch has, and it is the only one that will ever need replacing — creasing at the lug ends first, then darkening where it meets the skin. Against rose gold and diamonds, that shows sooner than it would on steel.
Helvetus straps are shaped for the Ballon Bleu case in 14 mm, 16 mm, 18 mm and 20 mm, so the leather meets the curve of the case cleanly instead of leaving the gap a generic band always leaves.
More than 50,000 customers worldwide, free shipping and free returns, and no import costs on any order, anywhere. Leather and crocodile straps are covered for one year; our rubber straps carry a lifetime warranty.
