Apiguard is a slow release thymol gel that is natural and non-toxic.  Average 93% efficacy rate.  Best results occur when bees are active and daily temperatures are between 60 and 105 degrees Farenheit.  Use 2 of the 50gm treatments 14 days apart to treat for Varroa mites as well as effectively treat for Tracheal mites.  The box of foil packs contains 10 50gram treatments that will treat 5 colonies.  The Bulk Tub contains 60 50gm doses.