This is a 4 pack of Uwell Caliburn A2 replacement cartridges. Each Caliburn A2 refillable pod has a 2ml e-liquid capacity and an atomizer resistance of 0.9ohm. Each pod can use salt nicotine e-liquid and can be refilled via the removable tip. It is a top fill system for easy top up. The drip tip also serves as a juice fill cover.