Ultherapy uses focused ultrasound targeting the 4.5 mm layer beneath the skin...

https://spark-wiki.win/index.php/Thread_Lift_Migration:_How_Common_Is_It_and_What_Does_It_Look_Like%3F

Ultherapy uses focused ultrasound targeting the 4.5 mm layer beneath the skin called SMAS, which few treatments reach. It triggers collagen buildup over 3 to 6 months for natural lift