Check the listing for details. JustiFLY 360 gm Horn Stable House Face Fly Cattle *6 Packages*. Condition: New. Listed at 103.45 USD. JustiFLY™ is an insect growth regulator (IGR) larvicide for use on the farm that effectively treats horn flies as well as disease-carrying face flies, biting stable flies, and nuisance houseflies. This add-pack is priced to allow beef and dairy producers cost-effective fly control by stopping the larvae from developing once in contact with treated manure. The add-pack provides full-season fly control while letting producers utilize their own specific mineral choice. No withdrawal period reduces animal handling stress. Approved for all beef and dairy calves and cows (including lactating cows). 12-oz. (360 g) add-pack for use with free-choice minerals to control flies on pasture and confinement cattle, one add-pack treats one 50-lb. bag of free-choice mineral. Active ingredient: Diflubenzuron.