Ultherapy uses ultrasound to target the 4.5 mm SMAS layer, making it popular...

https://fernandosgreatinsight.urbanvellum.com/posts/can-rf-tighten-skin-but-not-lift-what-does-that-mean

Ultherapy uses ultrasound to target the 4.5 mm SMAS layer, making it popular for lifting deep tissue without cutting. RF heats skin to around 40-45°C to boost collagen, great for mild tightening