Get continuous protection from flies with TERRO Fly Magnet Bait. Eliminating just one female fly can reduce the population by 150-500 flies per year. It can be used with all fly trap systems. When used with your compatible trap, the bait attracts a variety of common flies, including house flies, barn flies, and bottle flies, to drastically reduce fly populations around your home. It’s also easy to set up – just add the bait to your trap, fill the trap with water, and hang!