Python is a slow-release, plastic ear tag containing a synergized formulation of zeta-cypermethrin, a potent, enriched s-isomer pyrethroid compound. This insecticide has excellent activity against many pests, including horn flies that are resistant to certain other insecticides. A high loading of piperonyl butoxide synergizes this S-isomer and dramatically reduces the effect of pyrethroid resistance. Python's exclusive tri-polymer matrix of non-toxic inert ingredients delivers a high ratio of synergist to insecticide for maximum insect-killing action. Python has a net weight of 0.34 oz (9.5 g) per tag.