A diffuser head that fits on any hair dryer! Has a 2.25" flexible diameter for dryer attachment. Purchased from Ulta for $33. Barely used-- I chopped all my hair off shortly after buying it! "With a turn of the head, the Bio lonic's Universal Diffuser adjusts air flow based on your styling needs. Open vents for higher air flow or close them to be more targeted. 12 air outlets for faster drying."