The Bumble & bumble Thickening Serum is your ticket to thicker, stronger strands. Created especially for those with lifeless, fine & thinning hair, this nightly leave-in treatment will boost fullness. It fattens & fortifies the strands over time to boost natural thickness, resulting in some seriously glamorous hair. Before bed, dispense about 2 or 3 pumps of serum into the hands & work into the roots & through the hair. Those with longer hair may need a little more to make sure it's smoothed through right to the ends. If your hair is ultra fine, use twice daily.