I believe that a charm quilt uses no duplicates. But a regular quilt can have dups. I'm making a 2" postage stamp quilt; I started it months ago; so, it is a work in progress. I wanted it to be a charm one, but there is no way. So, there will be a few duplicates. The squares are so small, I'm sure they won't be noticable. I've traded with several people; still need quite a way to go....