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

https://rylansultimatethoughts.talesignal.com/posts/is-standard-hifu-safe-if-done-by-a-non-doctor-operator

Ultherapy uses focused ultrasound to target the 4.5 mm SMAS layer, reaching deeper than standard HIFU, which works around 1.5 mm. RF heats skin to 40-45°C to stimulate collagen more superficially