Used as the second step in the STS Express Smoothing system, Prosystem STS Express Design Essentials Smoothing Mousse Max Smooth 7.5 oz is infused with micro-fine amino acids to strengthen hair from root to tip while delivering anti-swelling and anti-reversion properties for a long lasting lustrous, frizz-free for up to 12 weeks. Prosystem STS Express Design Essentials Smoothing Mousse Max Smooth 7.5 oz is one of the safest smoothing technologies available as it is formaldehyde and formaldehyde derivative free, and infuse with silk protein to nourish and help repair the hair throughout the smoothing process.