I designed this model to use my old Bambu spool refill cardboard core as storage, also not limited to one, you can joint multiple cores together to make a taller box, great for pens or cans. 

The top and bottom can snap together , not loose fit, so it will stay in place. 

I have to leave enough tolerance because the variation of spool cores, which are made from cardboard.

You may need to press hard to put the on, but more likely you may need some drops of glue to make them stay, make sure you put the glue in the slot, press the cardboard in and then give a twist so the glue will apply evenly.

17g for the top ring, and 27g for the base, or if you want to connect multiple cardboards, the connector is 12 grams. 

Not bad for a super durable small box.