Fast-acting attractant (included) dissolves and activates when water is added. Draws 7 times more flies than flypaper. Durable plastic container holds up in sunlight, can be used again and again. Replace the used attractant with a refill packet in the trap to reuse. Environmentally safe, non-toxic mode of action, no poisons or killing agents. Intended for use outdoors. Effective for about 2 weeks.