some sites have it as 9.0mm but the one he is reffering is https://www.audemarspiguet.com/en/watch-collection/royal-oak/26510ST.OO.1220ST.01/
(i'm guessing) shows 8.85
they just keep getting thinner.. Rep makers need to step up their game =D
That's another model I meant this one: https://www.audemarspiguet.com/en/watch-collection/royal-oak/26522OR.OO.1220OR.01/