1.87% Ivermectin. Anthelmintic and boticide. Controls large and small strongyles, pinworms, ascarids, hairworms, large mouth stomach worms, lungworms, intestinal threadworms and bots. Proven safe for pregnant mares, breeding stallions and foals. Each syringe treats up to a 1250 lb. horse. Syringes are marked in 250 lb. increments.