The coil is where the wax is loaded, heated and vaporized. This is also the component that will need replacing first, and most often. Over time, coils burn out, so making sure replacements are available and affordable is important. Choices will include pancake style coils, wick, donut and rod coils - furthermore, dual rod coils and even quad rod coils exist, in both ceramic and quartz. It ultimately comes down to preference and budget.