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

https://reidscoolthoughtss.swiftnestly.com/posts/what-does-a-proper-assessment-look-like-before-skin-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