Purina's Wind and Rain(R)Storm(R)Fly Control mineral with Altosid(R)(Insect Growth Regulator) prevents the breeding of horn flies in the manure of treated cattle. Wind and Rain(R)Storm(R)cattle minerals' large particle size and special formulation keeps the mineral from absorbing water and blowing out of the feeder. Exclusive Storm(R)technology provides the ultimate in weather resistance to reduce waste and makes Wind and Rain(R)Storm(R)Formula more economical to feed than conventional loose minerals. | Purina - Wind and Rain Fly Control | Size 50 lbs