Keratin of hair is a beauty treatment that has become fashionable over the world that can repair the damage hair and correct your frizzy hair. Our factory use high-quality formaldehyde-free formula that can avoid the harmful to our health due to the formaldehyde cause. Of course, we also can add a small quantity of formaldehyde to make it better result according to customer demand. Doing one time, can keep more than 20 days.