Brush markers PRO contain 2.4ml of color each. They were produced with "liquid ink" technology, which means the intensity of color lasts through the last drop. They are twice as efficient as traditional filter markers. In addition, they are equipped with a Japanese super durable and flexible nylon tip. They contain non-toxic paints with an intense dye based color. The colors can be mixed, lightened and obtain tonal transitions by touching the ends of two different markers.