Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer, stimulating...

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, stimulating collagen deep beneath the skin. Unlike RF that heats surface layers to 40–45°C, Ultherapy works deeper for a gradual lift over 3 to 6 months