Melissa & Doug – Water Wow! Numbers – On the Go Travel Activity; This exciting activity book includes four reusable pages and a refillable water pen. Use the pen to fill in each activity, from coloring in counters to tracing numbers, and see hidden colors and pictures appear with every stroke! Then simply let the page dry to erase the pictures and fill it in again and again. This learn-to-count book includes numbers 1-20 to trace, alongside pictures of familiar objects to count. There are empty lines to practice writing the numerals, too! The chunky-sized water pen is easy for kids to hold and stores neatly right in the front cover.