The dark shaded cartridges have a slender and ergonomic mouthpiece attached. The refill is under a single-port plug that’s located near the top side of the cartridge. I’ve had no problems filling with any dropper. The cartridges have an adjustable airflow ring at their base where the coil heads screw in. Unfortunately, my airflow ring is positioned in such a way that I have to remove the cartridge from the housing to see where it’s set—the air slot is on the other side. But that takes only a couple of seconds to access and change it.
The two coils heads available for the Tix are a 0.8-ohm mesh coil and a 1.0-ohm regular coil. The mesh coil is optimally suited for a direct lung hit, and the 1.0-ohm coil is for a loose to tight MTL. However, you can still do a loose MTL on the mesh coils if you have to.