This model is in the form of a crystal Wine Glass, an attractive and seemingly innocent accessory. The wine glass design makes the switch possible by just twirling the stem between your fingers, as you wave your hand in front.
Some amazing transformation effects can be done with a mirror glass like visibly and instantly changing the color of a silk or ribbon placed in the clear glass. Or show a glass of ordinary water, and drop in a few shavings from a carrot. Cover this with a Hanky. Uncover the glass and show live Gold Fish swimming around in the water. This and much much more. The "innocent" nature of this prop makes it useful to every performer, for many types of effects, including kid shows, platform and stage magic, or mental magic.