For this trick, you'll need to borrow a ring from the audience. This way you'll be able to reassure them that there is no possible way any funny business is going on. You're going to mix the ring and the band together so much that they actually become one. Somehow, someway, you have interlocked the ring onto the band. When the spectator wants their ring back, all you have to do is snap your fingers and the ring is free once again.