The Nautilus 2S is a 2ml capacity tank, designed to be filled from the top. It comes with two coils: a 0.4ohm BVC coil and a 1.8ohm coil. The 0.4ohm coil is designed for more vapor production. While the 1.8ohm is designed for a smoother hit. Unscrew the top cap anti-clockwise a few turns, place your thumb on the top cap above the indicator spot and push away from you, this will reveal the filling slot. The longer drip is to provide more of a mouth to lung hit, while the shorter one is designed for straight to the lung hit.