Summary There are 2 marbles enclosed in the puzzle on a curved base. The goal is to get the marble in each of the two holes on either end. As always, there is a trick. Print base in a color Lid should be transparent Print or purchase 5/8" marbles Number 4 x 7/16" long screws used (x4) Modified designed based off Double Marble Puzzle by tomatoskins @ Instructables.https://www.instructables.com/id/Double-Marble-Puzzle/