The performer displays two boxes with lids, one red and one yellow. He also displays a solid multi color cube (shown on all 6 sides) and a number of small silks of different colors.
The two boxes are opened, shown empty, and the solid cube is placed in the yellow box which is closed. The silks are placed in the red box, which is closed. A magic pass is made, and when the yellow box is opened, the silks appear from it. Box is shown otherwise empty.
When the red box is opened, the solid cube appears from it, (again shown all six sides) and the box shown empty.
Instead of Silks you could use a sponge or rubber ball for the transposition or any other item that can fit in the cube.
You could also use the boxes as independent transformation effects. The yellow box can be used to transform the solid cube to any odd item (silks, balls, spring flowers, confetti etc.) that will fit in the cube. The red box can be used to change any odd items into a solid six sided cube.
The boxes are made from wood and are approximately 4″x 4″x 3.75″ in height.