Sorry but I'm going to contradict the above. Verm-X works as an intermediate wormer, between proper worming with Flubenvet. It won't tackle gapeworm and isn't totally effective on roundworm. But I suspect it solves the irritation of hair worm because we've noticed an improvement in poos after administration. One worm we did have which I can find no information on (about 2mm diameter and 20cm long coming from green eggs) infested an Orpington. The Flubenvet had no effect whatsoever but they were killed by Verm-X. As a result I've bought some more.