Over the years we've accumulated a number of white power cubes for various Apple devices (iPods, iPhones and our new iPad 2). I'm given to understand that the iPad requires a higher-power cube than the other devices take. Is there a quick way to tell the one for the iPad visually from the other cubes? Or do I need to get a magnifying glass and squint at the tiny gray text on the side of the cube? They all look fairly similar to me.