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

https://blogfreely.net/sordusgvrj/i-want-faster-results-should-i-combine-threads-and-ultherapy

Ultherapy uses focused ultrasound to target the SMAS layer at about 4.5 mm deep, stimulating natural collagen over 3 to 6 months. Unlike RF, which heats skin to 40 to 45°C mainly in the dermis, Ultherapy reaches deeper for lifting