1ml Black Ceramic Cartridge w/ 2mm inlet (100-pack)Ceramic Cell has revolutionized the cartridge industry. It is a great heating element for all different kinds of oils. This cartridge comes in an easy to fill 100 pack and is 1ml in size. Equipped with a black ceramic tip and 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