The basics Toppik Hair Fattener is a hair styling serum for fine or thin hair that adds volume and thickness while making hair shine. The benefits This hair styling product is formulated without sulfates and parabens. Safe for color-treated hair.  The uses The concentrated keratin formula has essential nutrients that maximize every hair strand, instantly creating noticeably fuller, thicker hair. The bottom line Now available in a sleek, new design with airless pump feature to make sure you always get the right amount of product with each use.