Easy application…Just shake, spray and go! Bosley Professional Strength Thickening Fibers are keratin fibers that bond securely to existing hair to blend and cover thinning and low density areas of hair for instant volume, thickness and fullness. Temporarily covers up roots and gray between color treatments. Long lasting, stays in place through humidity, wind and perspiration. Also use Bosley Professional Strength Non-Aerosol Hairspray & Fiber Hold Spray to provide extra durability and longer lasting results.