There are two refill systems: 
Depending on the design of the marker, different refill mechanisms can be used. A marker that can be screwed on at the mouthpiece can usually be refilled with both systems. A marker that cannot be screwed on, on the other hand, must be refilled with the capillary system. Ultimately, the choice of system is often a question of personal preference.

The capillary system:
With the capillary system, the marker is simply placed in the refill bottle with the tip down for at least one hour. After that, it is ready to write again. Clean and uncomplicated.

The drip system:
With the drip system, the marker is screwed on at the mouthpiece and the refill ink is dripped into the barrel by pipette. After screwing down, the marker is ready to write again. Very quickly.