This isn’t just any leave-in—it’s your hair’s ultimate shield. The STS Express Thermal Therapy Leave-In Sealant combines the power of keratin amino acids and panthenol to restore moisture balance, fight frizz, and fortify strands against heat styling and environmental stress. Designed to complement the full STS treatment, it seals the cuticle for a silky, shiny, and flawless finish. It’s the final step to smooth, protected, and truly radiant hair.