A soft pouch might be fine for carrying your device from the couch to the car, but if you travel a lot, get a hard case with separate compartments. You'll want slots for the device itself, spare cartridges, mouthpieces, and a small tool if you need to adjust anything.

The point is to keep the parts from knocking into each other. A loose coil in a pocket can easily scratch the finish on your device. And a cartridge with a glass tank can crack if it bangs against a metal body. Use the dividers—they're there for a reason.