Ultherapy uses ultrasound targeting the 4.5mm SMAS layer to stimulate collagen...

https://www.hometalk.com/member/254051008/alice1337254

Ultherapy uses ultrasound targeting the 4.5mm SMAS layer to stimulate collagen deep under the skin, with results peaking around 3 to 6 months. RF heats tissues to 40-45°C for surface tightening but doesn’t reach as deep