Rebuildable Dripping Atomiser or RDA have a deck in which you install coils, which is basically a metal wire wrapped round into a spiral shape. You would then slide cotton through the centre of the spiral. RDA’s have no tank, as the name states ‘dripping’ this is how you get juice into your coils, you drip through the top of drip tip or you can take the top cap off. In affect they are no different to the coils you would buy for a sub-ohm tank, for the exception of better taste. As the coils are usually installed horizontally, this allows more surface area for juice to be heated up.