These have quickly become a customer favorite. Easy to fill and they hold 2.0ml of e-liquid. Common 510 thread for use on all EGO and KGO type batteries. These are the long wick version (short wick version shown). To fill: Unscrew top metal part where the mouth piece is and drip liquid inside the tank, avoiding getting it inside the center air tube. Screw the top back on and you're good to go! DOA Warranty Policy: DOA Warranty Policy only on these units. Cartomizers, Crystalmizers & SV-Nova Tanks are disposable units.