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Marbles is a class of children's games played with glass, clay, or agate balls usually about ½ inch (1.25 cm) across. However, they may range from less than ¼ inch (0.635 cm) to over 3 inches (7.75 cm), while some art glass marbles for display purposes are over 12 inches (30 cm) wide. Marbles are often collected, both for nostalgia and for their aesthetic appeal. (wikipedia)