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

https://romeo-wiki.win/index.php/Is_Ultherapy_Backed_by_Real_Studies_or_Mostly_Marketing%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