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

https://helen-mitchell11.raindrop.page/bookmarks-74099039

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