Notice the column wheel mechanism visible from the dial side of the movement.
In Hublot’s Own Words:
“The Unico 2 caliber was designed to equip smaller chronographs and also open the world of Hublot to new enthusiasts. It retains the unique design of its former version with a double coupling system visible from the dial side as well as a 72-hour power reserve. But thanks to various technical optimizations, including the introduction of a new, flatter automatic winding system, it has been reduced by 1.3 mm in thickness.”