PYthon Dust in the only dust to contain two novel active ingredients for maximum efficacy against all major livestock ectoparasites. Zetacypermethrin is a 5th generation pyrethroid with enriched S-isomer content that is highly active against horn flies, face flies, ticks and other pests. Piperonyl butoxide is a mixed-function oxidase inhibitor that helps overcome metabolic resistance in insects and and synergizes the zetacypermethrin for maximum efficacy and residual activity. PYthon dust contains a photostable formula of piperonyl butoxide for long-lasting activity in sunlight. This 12.5# PYthon Dust refill (ONLY).