These are e-cigarette adapters.  An adapter will make your e-cigarette battery compatible with a different model’s atomizer.  If you’re curious about how your battery or atomizer will work with a part from another model this is the cheapest and easiest way to find out.  Some atomizers and batteries might seem to work better than others for you, now you can have the best of both worlds.

The battery is listed first and then the atomizer that would work with the adapter is listed second.  For example Selecto DSE901 to Exquisito DSE801 means that you would use a Selecto DSE901 battery and an Exquisito DSE801 atomizer together with this adapter.