Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer deep under...

https://technivorz.com/why-is-imaging-such-a-big-deal-in-ultrasound-skin-tightening/

Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer deep under your skin, encouraging natural collagen over 3 to 6 months. RF heats the surface to about 40 to 45°C for a quicker, milder firming effect