Gravity Feed Display Box. Fast-acting attractant dissolves and activates quickly once water is added. Proven to catch common nuisance or filth flies including house flies, cluster flies, false stable flies, blow flies, bottle flies,flesh flies and others. Place outdoors near household garbage bins, compost piles, dog kennels and other areas with flies. Sanitary; no need to touch the bait or the flies. Holds up to 20,000 flies.