Tip Diameter: 4.5mm (.18in)
Line Width: 2.5-3.0mm (.10-.12 in.)
Capacity: 17ml (.058 fl oz)

I have filled this paint marker with airbrush medium to convert any watercolor crayon, stick, pencil or pan into an acrylic paint.  The medium, when dry, is water resistant making your color stick and stay in a way watercolor normally does not (lack of acrylic binder)

The airbrush medium I'm filling the marker with is Golden brand Airbrush Medium.