Ultherapy uses focused ultrasound targeting the 4.5 mm SMAS layer for a precise...

https://landensnewperspective.hexaforgey.com/posts/what-does-mfu-v-stand-for-in-ultherapy-a-clear-guide-to-understanding-the-technology-behind-the-lift

Ultherapy uses focused ultrasound targeting the 4.5 mm SMAS layer for a precise lift that works deep under the skin