Markers can be refilled using the booster, dabbing the ink directly onto the nib or removing the nib with tweezers for quicker filling. Measures are marked on the bottle and the tip is angled for accurate filling. Refills offer the ability to custom mix colors. One bottle of permanent ink will refill a Ciao marker 13 times and a Sketch marker 8 to 10 times. Cleans up with rubbing alcohol.