How many apples? What kind? Any good eating apple will work. I used a large Gala. Fujis would work, as would many others. Don't use a red delicious. Don't buy them. They are awful, bred purely for appearance and shelf stability. If the apples you choose are large, one may well do. For smaller apples, use two. And honestly, if I had used one and a half of the nice, big Galas I had, it would have been a good call.