No other pour-on insecticide can provide the residual control of flies that is available with new CyLence Pour-On. Its active ingredient, cyfluthrin, is 4 to 6 times more active than older pyrethroid compounds. CyLence is proven effective on horn flies and face flies as well as biting and sucking lice, with no milk withdrawal for lactating animals. Ready-to-use. Dosages: Less than 400 lbs.– 4 ml., 400 to 800 lbs.– 8 ml., over 800 lbs.–12 ml.