There is a difference between carts, and cartos. Carts are cartidges which hold a small amount of liquid, and are used with atomizers, or attys, and are a 3-piece setup, battery, atty, cart. Cartos, or cartomizers, are one piece that holds the juice and has the atty inside, is a 2-piece setup, battery, carto. They also hold a lot more juice than carts. Sorry, I was getting confused so wasn't sure if anyone else was LOL