Non-toxic, water-based POSCA markers can be used on almost any surface so you can express your creativity freely. The alcohol- and solvent-free opaque paint covers well, is blendable, dries quickly and can be overlaid when dry. The pen has a valve mechanism for a tight paint seal and a ball inside the barrel that mixes the paint, allowing for even paint consistency, texture and continued optimal results. The pen tips can be rinsed with water and some are reversible. They can also be used like watercolor when mixed with water and a brush.