My Mister and I have used these Efest batteries for a good long time now. We both run single 18650 battery VW/ TC mods of various brands and these last a good long time both in terms of lifespan and discharge time. Never had a faulty one. We do look after them, charged in a proper charger, kept in cases and we always rewrap if the original wrap gets damaged. Service from Go Smoke Free was excellent, batteries were here in less than two working days and the price is fantastic. Will order again.