No mess No clean Disappear and use repeatedly Keep entertained on trip You fill the pen with water and just move it over the page. so no mess no drawing on walls or tables and anything else child can get his hands on. Once the water runs out just refill it and it's good to go. The pen does not leak, only takes 1-2 oz of water, doesn’t need refilled often, and stores right in the book cover. Colors of the pages are vibrant and reveal hidden images. Books are easily packed in a bag or carried by a child. 【Notice】 1. Don't put cards together if they are all wet. The white part will be easy comes off and sticks to the back of the other card.2. Before using, it is better to put the head of painting pen into the water to soak for 2-3 hours, then fitted it with water to use, it will not appear dripping phenomenon, and the reason for drip phenomenon of painting pen occurs, mainly due to the head of pen has no fully expanded, the above phenomenon will be occurred.3. Two drawing pens without pen cap is to avoid the risk of swallowing.4. If product defectives, we could replace new or refund all. If there is any problem please send email to us, we will help you solve issue within 24 hours.