Nuvo-Aqua Flow Pens: Summer Holiday. These pens are uniquely designed to create a watercolor effect without the hassle and mess. These highly pigmented water-based pens leave you with a bright, vibrant finish. The perfectly formed watercolor brush nib makes the pens extremely versatile and is perfect for adding small detail or color washing large areas. This package contains three 6-1/4 inch long pens in assorted colors. Conforms to ASTM D 4236. Imported.