These pre-filled 5.3 ml water-based Acrylic Paint Markers are non-refillable and work on a pump release system. They contain water-based colour which is streak-free and fast drying.5.3ml in each.2-3mm medium point spongy nib.Water-based.Colours are fully intermixable.For use on canvas paper and fabric as well as harder surfaces like glass wood ceramic and plastic.