The Cartier Ballon Bleu WSBB0073 is the current 28 mm Ballon Bleu on the interchangeable steel bracelet — the smallest, most delicate watch in the collection, and the reference you'll find on recent paperwork for the steel 28. Cartier makes two reference numbers for this exact watch, which confuses owners, and almost nothing online tells you which strap it takes. Both answers are below — along with a truth about small watches that most strap guides get backwards.
Cartier Ballon Bleu WSBB0073 Strap Size and Fit
The essentials:
- Reference: WSBB0073, Ballon Bleu de Cartier, 28 mm (28.6 mm case), quartz
- Correct strap size: 14 mm
On the product page, select the 14 mm option. The Ballon Bleu's case is convex in every direction with short curved lugs, so a strap shaped for this model sits flush where a generic flat strap gapes. Every Helvetus Ballon Bleu strap ships complete with its own steel buckle.
About the reference numbers: Cartier has used two numbers for the steel 28 on the bracelet — WSBB0067 and WSBB0073. They're the same 28.6 mm case, so both take 14 mm; whichever is on your papers, order the same size. And size by case, not by photos: the Ballon Bleu ladder runs 28 mm → 14 mm, 33 mm → 16 mm, 36 mm → 18 mm — the sizes are nearly impossible to tell apart on a screen.
Swapping off the bracelet: the interchangeable bracelet releases at the end link, and underneath sit conventional lugs on standard spring bars. Any watchmaker does the change in a minute, or you can with a basic spring-bar tool.
The Smallest Ballon Bleu
Everything that made the Ballon Bleu famous is here at its most concentrated: the round, pebble-like steel case, the fluted crown with its blue synthetic cabochon spinel floating in the guard, Roman numerals, blued-steel sword hands, sapphire crystal — all in 28.6 mm, running a quartz movement that just works. The dial is silvered opaline, smooth and soft rather than the guilloché of the larger sizes, and water resistance is 30 meters: a dress watch through and through.
The Small-Watch Rule Everyone Gets Backwards
Here's the counterintuitive part. People assume the smaller the watch, the smaller the strap decision. It's exactly the opposite. On a 42 mm watch, the case dominates and the strap is a supporting act. At 28 mm, the proportions flip — the strap makes up nearly half of what the eye sees on the wrist. No other Ballon Bleu owner gets as much visual change per strap as you do.
That makes the strap the boldest — and cheapest — styling decision available on this reference. These are the most popular choices among Ballon Bleu 28 owners:
1. Blue Leather – The Name, at the Size Where It Shows Most
The watch is named for blue — the spinel in the crown, the blued sword hands — and yet the steel-on-silver factory look keeps that color a secret. A blue leather strap for the Cartier Ballon Bleu makes it the theme, and at 28 mm the effect is bigger than on any larger size: the strap carries half the look, so the whole watch reads blue. The single most transformative choice for this reference.
2. Black Crocodile – The Texture the Dial Doesn't Have
The larger Ballon Bleus have guilloché dials that bring their own texture; the 28's opaline dial is deliberately smooth. That's exactly why a black crocodile strap works so well here — the scales add the richness the dial holds back, in miniature proportions that suit a small dress watch perfectly. The most formal way to wear the WSBB0073, and the classic pairing for evening.
3. Black Leather – The Everyday Dress Default
Simple, correct, endlessly wearable: a black leather strap turns the 28 into the quietest kind of elegant — and gives the polished bracelet its rest days, keeping it free of the hairline scratches daily wear collects. If the watch was a gift and you want it to stay looking exactly as it arrived, this is the strap that does it.
4. Blue Crocodile – The Dressed-Up Blue
Both ideas in this guide, combined: the collection's own color in the exotic texture the dial lacks. A blue crocodile strap is the occasion version of the hero pick — subtle at a distance, unmistakably deliberate up close.
Every compatible option in 14 mm is in the full Cartier Ballon Bleu strap collection.
Keep the Bracelet — and Its Links — Complete
Most owners of the 28 rotate: leather through the week, bracelet when they want it. If links were removed to size the bracelet, store them together — the interchangeable system makes links easy to remove and just as easy to lose, and a complete bracelet always matters most on a watch this current.
Final Thoughts
The WSBB0073 proves the smallest Cartier makes the biggest strap statement. Helvetus is one of the leading names in the aftermarket strap world, and our Ballon Bleu straps are shaped for the curved 28 mm case — an exact 14 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.
Half of what people see on your wrist is the strap. Choose it like it matters — because on this watch, it does most of all.
