AquaDoodle Magic Pens 2 Pack

My youngest son has the AquaDoodle Travel Do N Doodle Pad and the Musical AquaDoodle Mat.Each of these items came with one AquaDoodle Pen.However, after much play and several travel destinations my son has misplaced both of his pens.So when I saw the AquaDoodle Magic Pens 2 pack set I though that it would be a good idea to buy it.The pens are very simple to use. For the pens to work you take the top off and just add water. The water absorbs through the sponge at the tip of the pen.Once the sponge has enough water you can use the pen to write on any AquaDoodle surfaces.The images disappear from the boards or mats once the water drys.I have notices that the sponge at the tip of the pen has a tendency to harden once the water is absorbed out.