PRO LONGER concentrate 15 ml PRO LONGER concentrate 15 ml 15 ml of PRO LONGER concentrate is enough for up to 5 treatments. It can be mixed with other products to create a customized treatment for all hair types. The concentrate is designed to help hair look and feel fuller and longer. It can be applied to the roots and shaft of the hair to boost volume, length and texture. It can also be used to reduce breakage and improve hair's overall health.