L'Oréal Professionnel's Pro Longer multi-benefit leave in treatment helps to thicken your long hair whilst making it visibly healthier and stronger looking. When used with the Pro Longer shampoo for long hair, there is a 47% hair breakage reduction and split ends are reduced visibly by 41%*. The unique Filler A-100 technology works by penetrating the fiber core to plump and thicken the hair from the inside. Amino acids in the formula work to strengthen the hair from the outside. The formula works on thin ends, or areas where help is most needed. Instrumental test, after application of Shampoo + leave-on. At L’Oréal Professionnel, we are striving towards an ever more responsible and sustainable business model, transforming our activities to respect the planet’s limits. 100% recycled plastics are now prioritised in the manufacturing of our Serie Expert bottles, reducing the use of virgin plastics. The Serie Expert collection is produced in a facility that has been carbon-neutral since 2015, and has implemented a water recycling loop that has reduced water usage by 47% since 2005.