L’Oréal Professionnel Serie Expert Pro Longer, 150 ml, Hair Creams and Gels for Women, The L’Oréal Professionnel Serie Expert Pro Longer leave-in treatment gives your hair everything it needs after washing. Characteristics: effective protection during heat styling leaves hair shiny and hydrated smooths the hair fibre How to use: Apply to towel-dried hair. Do not rinse. Do not rinse.