Been buying these for years for various devices and am still amazed. even after all these years nothing can touch them for sheer efficiency. I vape these at 14 watts and gives me the same satisfaction as squonkers of old. I use these in a boro tank in a billet box and the battery life with these coils is phenomenal, I get 2-3 days battery life over 20_25ml of juice. Maximum flavor, cloud and battery life. Only negative is they last so long I get fed up of the juice and end up throwing them prematurely just to change flavor. for the price I can't even entertain cleaning and reusing. They last anywhere from 1wk to a month, it is entirely dependent on your juice. One caution is don't use at too high a wattage or they WILL burn