Our Premium Vea® cartomizers will hold approximately 1mL of juice for the first fill. This is about 40 drops from our dropper caps. If you're using a dropper cap start with 20 drops and allow the cartomizer to adsorb that. Observe the fiberfill, if the top looks dry add more drops. You will end up with 20-40 drops depending on the size of the drops. Additional refills may require less e-liquid.
If you continue to have problems refilling cartomizers, we recommend trying the Canteens.