Almost every Ballon Bleu has a silvered dial. That is the house look — guilloché, blued or steel hands, light and formal.
The W6920042 is the one that does not. Black guilloché dial, Roman numerals, steel sword hands, the blue spinel cabochon in the fluted crown sitting under its guard, in the full 42 mm steel case with the automatic calibre 049 behind it. It is the men's Ballon Bleu, and the black dial makes it read as a completely different watch to the silvered version — heavier, later in the evening, less jewellery and more watch.
That difference matters when you choose a strap, because a black dial opens up options the silvered Ballon Bleus never had.
Lug Width: the W6920042 takes a 20 mm strap
On the product page, select the 20 mm option.
The 42 mm Ballon Bleu case uses a 20 mm strap. That figure runs consistently across the size: independent strap-size charts, our own collection sizing, and the original Cartier strap dimensions for the 42 all land on 20 mm.
Two mechanical points for this reference specifically:
- Standard spring bars. The W6920042 is from the classic Ballon Bleu generation, before Cartier introduced the interchangeable bracelet system. There is no proprietary quick-change fitting to work around — a spring bar tool, or our installation tool, is all you need.
- Your Cartier clasp still works. Our Ballon Bleu straps are made to be compatible with the original buckle, so if you have the Cartier deployant you can keep using it.
The Ballon Bleu size ladder
The Ballon Bleu spans four case sizes and each one takes a different strap:
| Case | Strap size |
|---|---|
| 42 mm (W6920042) | 20 mm |
| 36 mm | 18 mm |
| 33 mm | 16 mm |
| 28 mm | 14 mm |
If your case is 42 mm with the date at 3 o'clock, you are on 20 mm.
Why this one wears better on leather than most Ballon Bleus
There is a practical argument and an aesthetic one.
The practical one is weight. The 42 is around 13 mm thick with a domed case and a full steel bracelet, and that adds up to a watch that makes itself known by mid-afternoon. Moving it onto leather takes a noticeable amount of mass off the wrist and lets the case sit closer to it, which changes how the watch feels far more than it changes how it looks. Owners who find the 42 slightly too much watch on the bracelet often find leather solves it entirely.
The aesthetic one is the dial. On a silvered Ballon Bleu, every strap is a contrast — there is nothing on the watch for it to agree with. On the black-dial version you can go tonal, and the watch becomes one continuous object from the crown to the buckle. That is not an option the rest of the collection gives you.
And the usual argument still applies: the polished centre links of a Ballon Bleu bracelet are the first thing on the watch to look tired. Time spent on a strap is time the bracelet is not collecting scratches.
The four best straps for the W6920042
1. Black crocodile — the tonal option, and the best-looking one
Black Crocodile Strap for Cartier Ballon Bleu
This is the pairing the black dial was waiting for. Dial and strap share the same colour, so nothing interrupts the eye travelling down the wrist — and the crocodile texture supplies exactly the kind of detail the guilloché dial already has, so the two answer each other instead of competing. On a 42 mm case it looks expensive in a way a smooth strap does not quite manage. If you buy one strap for this watch, this is the one.
2. Brown leather — the version you wear on a Tuesday
Brown Leather Strap for Cartier Ballon Bleu
Black and steel is a formal combination whether you intend it or not. Brown breaks that up: it warms the case, softens the black dial, and turns a watch that reads as evening-wear into something that works with a jumper on a Saturday. It is the strap most owners buy second, and quite a few end up wearing it more than the first.
3. Blue crocodile — the colour the watch is named after
Blue Crocodile Strap for Cartier Ballon Bleu
There is already blue on this watch: the spinel cabochon set into the crown, sitting in plain view under the guard. A blue crocodile strap picks it up and makes the detail deliberate rather than incidental — and against a black dial, blue reads as rich rather than bright. It is the most distinctive thing you can do to a W6920042 without it ever looking like a costume.
4. Black leather — the quiet version of pick one
Black Leather Strap for Cartier Ballon Bleu
Same tonal logic, none of the texture. Smooth black leather is the most understated way to wear this reference: the watch reads as a single dark shape with a steel case around it, and nothing on the wrist asks for attention. It is also the easiest strap to live with — it goes with a suit and it goes with everything else.
Every colour and size is in the Cartier Ballon Bleu strap collection.
Fit, in one line
Order 20 mm, keep your Cartier deployant or choose a buckle, and fit it with standard spring bars.
More Cartier strap guides
Made for the Ballon Bleu, not adapted to it
Helvetus straps are cut for one watch at a time. Our Ballon Bleu straps are shaped for the case in 14 mm, 16 mm, 18 mm and 20 mm, so the strap meets the curve of the case cleanly instead of leaving the gap a generic band always leaves — and they work with the Cartier clasp you already own.
More than 50,000 customers worldwide, free shipping and free returns, and no import costs on any order, anywhere. Leather straps are covered for one year; our rubber straps carry a lifetime warranty.
