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

https://reidscoolthoughtss.swiftnestly.com/posts/what-does-a-proper-assessment-look-like-before-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