A total of 12 books: 2 volumes of Invention Showdown and 10 volumes of Experiment Showdown. None of them have covers. There are traces of name stickers on some of the books. There are many instances of folded covers, stains, pen marks, sun fading, and damage to corners and edges, in addition to what is shown in the photos. Experiment Showdown, a learning competition, offers fun content for learning about experiments and biology. - Series Name: Learning Competition - Series Name: Experiment Showdown Series Inspiration Showdown, Invention Showdown Series Educational Manga Thank you for looking.