Based off of the original one I got when I was about 6. This thing is a work in progress, and there may be some quirks to be sorted out if this is printed. Don't have a printer? Check out my Shapeways Shop here- https://www.shapeways.com/shops/MiniFidgets This model is imperfect, you will need to hold the lower piece on when sliding the inside out. A Version two is in the works.