Sakura-Koi Coloring Brush Pens. Coloring your artwork is easy, anywhere, anytime with the no-mess, dye-based, Koi Coloring Brush pens. These pens perform similar to an artist brush. Make fine, medium or bold brush strokes just by changing the amount of pressure to the nib. The durable tip will quickly spring back to its original shape. The odorless, water-based solvent facilitates smooth blending and layering of colors. Koi Coloring Brushes are a convenient way to add vibrant color to any sketch, journal, cartoon, illustration or rubber stamps. This package contains six 5-1/4 inch long watercolor brush pens in six different colors. Conforms to ASTM D 4236. Imported.