Rainbow Arch Essential Oil Air Vent Diffuser HOW TO: Clip your wood diffuser to your car air vent and add 1-2 essential oil to the fiber to enjoy the aroma while driving. Add more oils as the scent fades. This will work with either Vertical or Horizontal air vents PLEASE NOTE: All designs are handcrafted and one of a kind. Not one wood piece looks the same, they are all uniquely handcrafted. CARE: The air vents are solid wood. To get the longest life out of them, please handle with care. Unnecessary rough handling can result with them cracking/splitting along the grain.