Ultherapy uses focused ultrasound targeting the 4.5 mm SMAS layer for deep skin...

https://sophiasbestchat.capitaljays.com/posts/thread-lift-results-last-12-to-18-months-what-happens-after

Ultherapy uses focused ultrasound targeting the 4.5 mm SMAS layer for deep skin tightening, with results peaking around 3 to 6 months. RF heats the skin at 40 to 45°C to boost collagen more superficially and often requires multiple sessions