Coil Head Replacement Packs (aka atomizer heads) are for your clearomizers. Instead of needing to dispose of the whole clearomizer unit when the coil becomes burnt out or dead, simply unscrew the coil head and replace it.
Coil Pack Compatibility:
Older generation clearomizers are not built with replaceable coil technology, but in recent times and increasing number of them allow the user to change the atomizer head. On this page you can find a growing range of those which do.
Changing the coil couldn't be easier. Simply unscrew the base of your clearomizer and you should be able to see the coil head at the bottom. Unscrew this little unit (it will be indentical to the coil head you are going to replace it with) and screw in the fresh one. It's a good idea to have a tissue to hand so as not to get e-liquid on your hands.
In time, all clearomizers above a certain size will have the facility to replace the coil, but at present, it's mainly the Chinese brands that allow it, plus an increasing number of UK ecig brands.