Infused with Biotin and Zinc PCA, our Densifying Spray Treatment for thin hair works on the surface of each strand to instantly expand the diameter by up to 9% for the sensation of up to 9,000 more strands after one use. How To Use: Step 1: Apply the Biolage Full Density Thickening Shampoo to damp hair. Massage into a lather. Rinse Thouroughly. Step 2: Apply and distribute the Biolage Full Density Thickening Conditioner evenly through hair. Rinse thoroughly. Step 3: For maximum extra thickening results, use the Biolage Densifying Spray Treatment to instantly work on the surface of existing strands and expand the hair diameter.