I've been working on paper folding toys recently, including a hexaflexagon for a dinner party last weekend (coming soon to a Bouncin' Dog near you!). One of the toys is a pop-up cube we were introduced to while visiting the Drachen Foundation last year (some day the cube will also be at Bouncin' Dog). The "power" for the cube is a rubber band, which has to be a specific size. Did you know that there is a standard for rubber bands?