Everyone needs the ability to stick a whiteboard marker to the front of their fridge. Everyone needs a rocket. Now you can have both in the one convenient package.It's currently set up for a whiteboard marker that has some taper to the body, between 15-17mm diameter. If your pens have a different diameter, edit the appropriate parameters in the scad file to suit.Print it out. Stick a disc magnet (dealextreme.com may be your friend in this department) to the back with some hot glue. When cooled, attach to the fridge.