These are XL dual coil cartomizers for the 510 connector. They have two coils in parallel for a resistance of 1.6 ohm. Nice warm vapor and throat hit. They seem to work well with voltages above 4v without a burnt taste. The clear ones have a plastic tube, black ones have a metal tube. It holds about 1.5ml of juice. The fill kit makes these easier to fill. Not to be used with regular 510 or ego batteries. We recommend high drain batteries if using in the little sister, big brother or big daddy. Price is for a pack of 5