One of three ingredients in our patented, stinky, flies-love-it formula, Ammonium Carbonate can be mixed with Active Dry Yeast and water to create a brew that flies can't resist. While any substantially stinky bait will work in our fly traps we have found this combination to be highly effective. Our pre-mixed bait is comprised of 1 oz. Ammonium Carbonate and 2 lb. Active Dry yeast. Add water to this mix and this bait is ready to attract flies for up to three months. We offer apre-mixed 3 month supply or you may purchase the ingredients separately.