The Macbeth manual specifies the Kodak check plaque, so that is what I was looking for. The Stouffer products are much cheaper, but I have no way of knowing for certain if they are the equivalent of the Kodak product. One source I contacted told me that you have to have the check plaque recommended by the manufacturer, and in some cases they are proprietary products. I suspect, in the end, they are all pretty close to the same.