Hang SHU-FLY 3 feet to 10 feet from opening where flies are entering. Hang SHU-FLY pouch from 5 to 6 feet from ground or floor. Adjust height for best results. In patio and outside areas, hang SHU-FLY pouches 8 feet to 12 feet apart. It's the principle of reflection.
Humans have one lens in each eye.
Flies have 800 lenses in each eye and that makes them ultra-sensitive to light.