Give the kids something fun to open.  This is a Maze Can of about 3" ID and roughly 1.25" high.  There are 3 tabs inside the lid that mate up with 3 identical maze pathways on the core.  There are 3 dimples on the outside of the lid to show where the tabs are on the inside.  This should be printed out in PLA for rigidity.  If you use nylon, PETG or some other flexible filament, the lid will squeeze and it will pop out of the track.  

It is highly recommended that you set your outside perimeter layers in your slicer program to print very slowly (20-30 mm/s) and the inside fill you can print up to 70 mm/s.  The reason is that if you print fast, the maze pattern gets a little exaggerated and swells to the outside requiring a lot of sanding of the OD of the core to get the cap to go over without interference.  When I printed the both pieces entirely at 70 mm/s, I needed to do a lot of sanding to clean up the OD of the core and the maze pathways.  When I set the outside perimeter print speed down to 25 mm/s, there was hardly any clean up required and the tabs moved through the paths fine and the cap fit over the core with no problems.  Be prepared to sand any abnormality off the sides.  It is also recommended to put a little lubricant like Vaseline in the maze track since PLA doesn't like to slide on itself well.   It is hard to make mating parts work on every different printer, but slower speeds are always best on parts that have to mate together.  I filled them full of candy and gave to the grandkids to play with.  They loved them.  Each of them had to have their own color.  See the included documentation for maze layout.