These dual brush pens have a versatile flexible nylon fiber brush tip on 1 end that creates medium or bold strokes simply changing brush pressure. fine tip other end is for smooth straight lines or . resilient nylon brush retains its point, stroke after stroke. ink is water-based blendable: use 2 together, or use the colorless blender pen. The pen tips self-clean after blending so there is no messy clean-! Use these pens for coloring, rubber stamping, hand-lettering, doodling, journaling, and more. Perfect for fine techniques. ink is acid-free, non-toxic, odorless, non-bleeding. Each package contains 10 pens (9 colored, 1 colorless). Available in a variety color schemes, each sold separately. Conforms ASTM D 4236.