Screw-in cartomizers are typically pre-filled electronic cigarette cartridges that are bought to refill your e-cigarette after your initial starter kit has run out.
The overwhelming benefit of refill cartridges is that they make vaping (the act of 'smoking' an electronic cigarette) incredibly cheap. Once you have paid for your initial e-cigarette starter kit, you only need to get more refills from then on (until the battery on your e-cig starter kit dies, which can take over six months). Cartomizer refills come in anything from packs of three to packs of six.
The Electric Tobacconist vape shop has the broadest range of e-cigarette brands in America and possibly the world. To fill up your e-cigarette (depending on the type you have), you can also discover vape juice in many nicotine levels or flavors