Enriched with Filler-A100 and Amino Acid, the Serie Expert Pro Longer Ends Filler Concentrate Single Dose is the go-to treatment for long hair suffering from thin ends. Thanks to the high concentration of the patented Filler-A100 molecule, this disruptive professional formula provides strength and durable thickness to ends.€‹ When used with the Pro Longer shampoo and Mask for long hair, there is a hair breakage reduction*. The Filler A-100 technology is patented to L’Oréal Professionnel, and it works by penetrating the fiber core to plump and thicken the hair from the inside. The formula works on thin ends, or areas where help is most needed. *instrumental test, after application of Shampoo + mask + concentrate. Once a week, replace the Lengths Renewing Conditioner or Masque with the Single Dose Concentrate.