The AE2200 Low-E CARD is a disposable model that will allow 1,000 tests to be conducted. It will confirm if there is a Low-E coating present on the piece of glass you place it against. The AE2200 will test both sides of the piece of glass from one side. It will not differentiate which side has the coating but it will confirm if a Low-E coating is present. There are no metal contacts to scratch the glass surface. Therefore it is safe to use on all glass, even if the glass is dirty or has a label or other insulating layer on it. After 1,000 tests, simply dispose of the card.