I think they’re 0.85mm, which is a pain. I’ve replaced them using generic 0.9mm pins with corresponding tubes that are thinner than the originals, giving the correct OD to fit the links and the correct ID to fit the oversize pins. Cutting the small tubes to fit is fun!
None of this would be necessary if Swatch Group would simply make the parts available at sensible prices, but the use of oversize pins/tubes can be a useful way of addressing wear problems.