Montblanc installed a large, massy, screw balance in the Heritage Chronométrie ExoTourbillon Chronograph. In a traditional tourbillon construction, this large balance would require a correspondingly large and heavy rotating cage. But the innovative mechanism of the ExoTourbillon solves this problem by isolating the screw balance from
the rotating cage. The cage is smaller than the balance, which oscillates outside the rotating carriage and on a higher plane. The screw balance is borne between two jewels, while the tourbillon is neither cantilevered nor sandwiched between two bridges, but turns in a two-point bearing at the foot of its staff. The advantage of this construction is that a smaller rotating cage has less mass so it needs less energy to support its rotary motion.
The Millenary 