No need to refill or change cartridges. The ink will last per omnia saecula saeculorum. Water is taken from humidity in the air and then is mixed with a special stone placed inside named Donaunite, which grows naturally in Donau river.
Nib is made with special 96 k gold, discovered recently with Alchemy techniques mixing gold and lotus flower. The result, lotus gold, is the best for nib in fountain pen.
An 8 holes wheel allows to change the ink/water flow, producing several levels of blue.