Marble Run Duplo Adapter (Duplo Bottom/Tube Top)

Works with the Marble Genius brand marble run, but it will work with other similar sets as well.  Just make sure the top of one of your tubes is approximately 23.6mm in diameter.

This adapter allows you to stick marble run pieces on top of Duplo blocks.  See https://www.printables.com/model/806549-marble-run-duplo-adapter-tube-bottomduplo-top for the opposite.

This block is very short to make the print time as quick as possible.  I printed with a brim, but no supports.

I made a Frankenstein's monster by sewing the bottom of the Duplo block to the top of the marble jump ramp.  I also shortened the entire block to reduce print time and adjusted a lot of the chamfers.