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

https://sophiasbestchat.capitaljays.com/posts/thread-lift-results-last-12-to-18-months-what-happens-after

Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer deep under your skin, giving a firmer, lifted look that unfolds over 3 to 6 months. Compared to RF heating the surface skin at 40 to 45°C, Ultherapy reaches deeper layers