Deerfly Patches are a non chemical, odorless protection from biting deerflies. They are a disposable 2 inch x 6 inch adhesive patch that is placed on the back of the hat or cap and trap the deerflies as they buzz around your head. Virtually every deerfly will land on the patch because they target it as a good biting place. Deerflies, sometimes called Marsh Flies, Sheep Flies, May flies, Sand Flies, or Greenheads bite hard. Conventional repellents do not work well on them. Used by gardeners, fishermen, hikers, campers, runners, bikers, canoeists, horseback riders, anyone outside. Field tested and recommended by Ohio State University, and the Michigan Department of Fish and Wildlife. One patch will last all day on your cap. Shelf life in the package, several years'