This simple sack stands up while you pack it, then it folds and stows away. The small size (7-3/4in x 7-3/4in x 4-1/2in) is a great size for a lunch bag. The medium size (12in x 12in x 7-1/2in) is about half the size of a grocery bag. The large size (14-1/2in x 13in x 9-1/2in) fits a 9in x 13in pan perfectly.