These are a pair of boxes approximately 1.5" in size. The magician opens a black box, and inside is the red box. Obviously the red box is smaller than the black box. The red box is removed. The box is finally shown empty. You now close the black box, put it into the red box, and close the red box. Obviously the black box is now smaller than the red box. This can be repeated as often as you like. In-n-outer boxes work on an ingenious geometric principle. The boxes are completely solid and rigid. They are not flexible, or elastic, and there are no sliding or moving parts, trap doors, substitutions or any such subterfuges. The boxes are ready to perform. VERY easy to do.