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

https://archeredxm754.timeforchangecounselling.com/does-ultherapy-help-with-skin-texture-or-only-lifting

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