This is a visual and impromptu routine using any borrowed dice. It is based on Les Scheyer's “A Dice Interlude” but uses a slightly simpler method and an additional backward phase.
You begin by explaining that the best way to tell if a set of dice are real and not tampered with is to add up the opposite sides of the dice to make sure that they all total to seven.
You then explain that even using real dice a sleight of hand artist can make you see any number they like. You demonstrate this by showing that the dice have one, two, three, four, five, and six on opposite sides. To further prove your point, you go backwards by showing 6-5-4-3-2-1 on opposite sides instead of the known numbers.
You can immediately let everything be examined and even give the dice as gifts.