A rebuildable atomizer is not like a regular tank that you insert pre-made coils into, instead the user builds/wraps coils and installs them into positive and negative terminals (the build deck). Once the coils are installed the user must also install the wick, which consists of threading cotton through the center of the coil. Because the user is not restricted to a certain type of coil provided by a manufacturer, he/she has a lot more freedom in terms of coil resistance, wicking, wattage, etc. The number of coils in atomizer houses ranges from one and all the way up to eight or so in some specialty atomizers, they are usually single or dual coil though. Using a rebuildable will provide the best flavor you can get from a vaping device.