Ultherapy uses ultrasound to target the 4.5 mm SMAS layer, stimulating collagen...

https://bizzmarkblog.com/is-ultherapy-fda-cleared-for-lifting-or-just-tightening/

Ultherapy uses ultrasound to target the 4.5 mm SMAS layer, stimulating collagen deep under the skin. It’s known for precise depth control and visible results that develop over 3 to 6 months