Fleer, Topps, ALOU, ERA, and Wagner are all big names in the baseball card industry. FLEER and Topps are two of the most well-known card companies, while ALOU, ERA, and Wagner are all famous players whose cards have been produced by these companies. ALOU was a Dominican professional baseball player who played for the Montreal Expos, San Francisco Giants, Chicago Cubs, and New York Mets. ERA stands for Earned Run Average, which is a statistic used to measure the effectiveness of a pitcher. Wagner was an American professional baseball player who played for the Pittsburgh Pirates and Boston Braves.