Package contains, 1 special fiberglass cylinder, 1 wooden stake, hardware, 2 clear sticky sleeves………….. How It Works: Dr. D.F. Williams (USDA) discovered that Biting Flies were attracted to a special type of fiberglass panel when sunlight was reflected thru it. The panel has a clear sleeve with a non toxic sticky surface facing out to capture the biting flies. Replacement sleeves are available. It’s just that simple and very effective.