Tombow Dual Brush Pens are available in 108 colors and have two tips - one fine bullet tip and one high-quality, flexible brush tip. Use the fine tip for details or fine lines. Use brush tip for painted effects, and for extremely varied lines. Their water-based and water-soluble ink can be blended easily with water or make custom mixes with other colors. They are acid-free, non-toxic, and odorless.