The lightweight laptop is exactly as thin as the ZenBook 3 UX490UA but with improved cooling and a unique hinge setup. Asus is promising better ergonomics and external GPU (eGPU) support via its integrated Thunderbolt 3 ports. The system launches in one week for $1200 USD.
https://www.notebookcheck.net/Asus-shows-off-12-9-mm-thin-ZenBook-S-UX391-with-unique-ErgoLift-hinges-for-1200-USD.307854.0.html