From the manufacturer:
Experience no-mess painting--and learning--for kids on the go! This exciting paint-with-water coloring book includes four reusable pages and a refillable no-leak water pen. Use the pen and watch details and vibrant color appear with every stroke! Then, let the page dry to "erase" the pictures, and fill it in again and again. Explore a different color, circles, triangles, squares, and rectangles, and search-and-find activities on each page. The chunky-sized water pen is easy for kids three and older to hold and stores neatly in the front cover, so Water WOW books make ideal travel activity books for kids!