The CE range of clearomizers is very popular due to a few reasons. The main one is that they are easy to fill with e-liquid as they have a wide body and clear view so contents can be viewed. Another positive reason is that they have a large tank capacity, so less filling is required.
The way they work is via an internal dual wick system. The wicks absorb the e-liquid that is filled into the cartomizer and transfer the e-juice into the internal atomizer system inside the middle of the unit. The liquid is the vaporised upon drawing into the subjects mouth as they activate the battery.
The main difference between the two is that the CE5 can have the internal atomizer and wicks replaced. The CE4 is one whole unit and needs replacing altogether when it becomes redundant.
To replace the internal atomizer in the CE5, simply unscrew the base of the unit, carefully remove the atomizer wick system off the air chamber, and discard. Attach the new atomizer to the base of the air chamber, and re-screw the base into place. Fill with e-liquid as per the instructions above.