We use Revolution (cat sized, 5-15 lb) for all four of our ferrets during most of the year, in the months when mosquitos are out (since they transmit heartworm). One tube per ferret, once per month. Kills earmites within 24 hours and also prevents heartworm, fleas, ticks. It's very easy to use (have the vet show you how - just apply to skin on back of neck). You can compare prices online, but we get it from 1800petmeds.com, who has matched the lowest online price I could find. Free shipping, too. Jeff In Memory of Neo Caring for Trinny, Morphy, Baby Girl, and Luna [Posted in FML 5894]