The Catchmaster Fly Trap is safe and easy to use with no chemicals or pesticides. It contains an attractive lure that will attract most nuisance fly species. Just add water to the bag and the attractant will dissolve and lure flies within minutes. Works best when hung outdoors in the sunlight near decks patios nearby trees or when camping or enjoying other outdoor activities. Once the bag is full of flies it can be sealed and discarded easily. A special locking cap feature ensures that the bag contents will not spill or emit unwanted odors. Each bag comes with a special pop cap and twist tie for hanging.