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

https://fernandosnicethoughtss.scriblorax.com/posts/thread-lift-migration-how-common-is-it-and-what-does-it-look-like

Ultherapy uses focused ultrasound at 4.5 mm to target the SMAS layer, stimulating collagen deep within for natural lift over 3 to 6 months. Compared to RF, which heats skin at 40-45°C mainly for surface tightening, Ultherapy reaches deeper layers