This is a modification of the existing box designed for 1/4 inch magnets http://www.thingiverse.com/thing:769184 . Unfortunate for me, Hobby Lobby sells 1/4 inch magnets that are 8mm in diameter?!! I didn't even notice this until I had the lid built and could not get the magnets to fit. The label on the package is clearly marked 0.25 inch (8mm) magnets. So I brought the project into Fusion 360 and changed the size of the holes.