This needle attaches to a bottle of Various Ink refill and allows for precise, clean marker refilling. On a Copic marker, this needle can then be inserted along the broad nib. On Sketch, Ciao, or Wide markers the nib needs to be removed before inserting the Booster needle into the marker.
Boosters are reusable and can be cleaned with a few drops of blender solution or rubbing alcohol. Always clean thoroughly between colors.