The Cartier Ballon Bleu W4BB0036 is the 36mm with diamonds in two places: 54 brilliant-cut stones around the bezel, and 21 more set into the silvered sunray dial itself — where they do something no other diamonds on a Ballon Bleu do. They mark the hours. On this reference, the jewelry is the watch face: you read the time by diamonds.
That one fact should drive every strap decision you make for this watch. Correct size first.
Cartier Ballon Bleu W4BB0036 Strap Size and Fit
The essentials:
- Reference: W4BB0036, Ballon Bleu de Cartier, 36 mm steel case, automatic
- Correct strap size: 18 mm
On the product page, select the 18 mm option. The Ballon Bleu's case curves in every direction with short, tucked lugs, so a strap shaped for this model sits flush where a generic flat strap leaves a gap. Every Helvetus Ballon Bleu strap ships complete with its own steel buckle.
Swapping off the bracelet: the interchangeable steel bracelet releases at the end link; underneath sit conventional lugs on standard spring bars — a minute's work for any watchmaker or a basic spring-bar tool.
Size by case, not by sparkle: every 36 mm Ballon Bleu — diamond-set or plain — takes 18 mm. The ladder runs 28 mm → 14 mm, 33 mm → 16 mm, 36 mm → 18 mm, and the sizes are nearly impossible to tell apart in photos. The 33 mm diamond versions take 16 mm; if you're unsure which you own, measure the case.
The Ballon Bleu That Tells Time in Diamonds
Everything signature is here: the rounded steel case, the fluted crown with its blue spinel cabochon floating in the guard, blued-steel sword hands, sapphire crystal, an automatic movement, 30 meters of water resistance. Then Cartier added the stones — a full diamond ring on the bezel, and on the dial, brilliant-cut diamonds standing in as hour markers across the sunray silver surface.
That second decision is the interesting one. On most diamond watches, the stones are decoration around the information. Here they are the information — twelve points of light your eye finds every time it checks the hour. Which means this dial has a property no plain Ballon Bleu has: it performs best against contrast.
Make the Hours the Brightest Thing on Your Wrist
Here's the practical truth about wearing the W4BB0036 on its polished bracelet: steel links flash, and every flash competes with the twenty-one small stones doing the actual work on the dial. Put the watch on a dark, quiet strap and the hierarchy corrects itself — the bezel becomes a clean ring of light, and the diamond hour markers become the sharpest points in view. The watch gets more legible and more beautiful at the same time, which almost never happens.
These are the most popular strap choices among diamond Ballon Bleu owners:
1. Black Leather – Read the Time by Diamonds
A black leather strap for the Cartier Ballon Bleu is the definitive strap for this reference: matte black beneath the case removes every competing gleam, so the 54 bezel stones frame the dial and the 21 hour markers snap into focus like stars after the lights go out. It's the jeweler's-tray principle applied to a watch you actually read. Smooth, formal, endlessly wearable — if this reference gets one strap, it's this one.
2. Blue Leather – Cool on Cool
The W4BB0036 already runs cold: icy diamonds, blued-steel hands, the blue spinel in the crown. A blue leather strap carries that temperature down the wrist — navy deepens the silver dial, keeps the stones the brightest element, and reads quietly expensive rather than showy. The choice for owners who want the diamonds discovered, not announced.
3. Black Crocodile – Evenings, With Texture Beneath the Stones
For occasions, a black crocodile strap adds the exotic register a diamond watch deserves at night — with the discipline that matters here: dark and tonal, so the croc's scales give texture beneath the stones without ever out-sparkling them. The most formal way to wear this reference.
4. Blue Crocodile – The Dressed-Up Cool
Both ideas at once: the watch's own cool palette, in evening texture. A blue crocodile strap is the occasion version of the blue pick — subtle at a distance, unmistakably deliberate up close, and still no match for the dial's own light, which is exactly the point.
Every compatible option in 18 mm is in the full Cartier Ballon Bleu strap collection.
Keep the Bracelet Perfect
If the bracelet came with your W4BB0036, straps are also how you preserve it: polished links collect hairline scratches from desks and daily wear, and on a diamond reference an unmarked factory bracelet matters most of all. Wear leather through the week, bring the bracelet out when you want it, and store any removed links with it — a complete set always holds its value best.
Final Thoughts
The W4BB0036 does something rare: it makes diamonds useful. The strap decides how well they do their job. Helvetus is one of the leading names in the aftermarket strap world, and our Ballon Bleu straps are shaped for the curved 36 mm case — an exact 18 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 set the hours in diamonds. The right strap is how you make them shine.
