I remember back in the day how when we went to the drive-in movies in the summer we would go to the snack bar and buy these little green coils that we would put in the rear window and light to keep away the mosquitoes. They would do a slow burn and leave the powdery ash just like incense does and had a slightly acrid aroma that still smells like drive-in movies in the summer to me. Well now PIC has brought back these same mosquito repellant coils along with a ventilated clay burner dish with a lid to use in the backyard, at campsites, on the patio or deck or even at a drive-in movie if you can find one of those anymore. I use them on my deck and I do think they help keep the buzzing pests away. One coil burns for 5-7 hours. It is probably not as effective in a large open area unless you use more than one but if nothing else, it is fun to use for the memories it brings back.