Ceramic Cell has revolutionized the cartridge industry. It is a great heating element for all different kinds of oils. This cartridge comes individually packed and is 1ml in size. Equipped with a white ceramic mouth piece and has a 2mm inlet.
1.2mm inlet - 2 small holes (best for thinner oils)
1.6mm inlet- 4 larger holes than 1.2mm (better for thicker oils)
2.0mm inlet - 4 larger holes than 1.2mm, and the diameter hole in the main shaft seemed more open as well compared to the 1.6mm inlet. (best for thicker oils)
If the oil that you are wanting to fill the cartridges with has a very thin consistency, then smaller 1.2mm Oil Intake Hole Size would be the best route. But if the consistency of the oil is really thick, then you should consider the 1.6 mm-2mm cartridges.
The little holes on the inside of the cartridge vary in size and quantity depending on the type of cartridge and oil that will be used. More holes and larger holes are better for thicker oils.