Maxello Magic

You can just wear the ring and show it as an optical illusion. During a trick you can turn the ring to shrink a card or make a coin shrink or turn to a larger denomination, use instead of a magic wand. Explain how your rings kept falling off your finger until you found this "self adjusting" ring.

"I just turn it until it fits me!" If you play Santa, an elf or leprechaun you can say that the ring gives you the power to shrink. But only on certain days! The ring can be used for a marketing campaign "Watch your business GROW!" (Or Shrink...) Great for a ring on rope routine!