The most common oversize wine bottle you're likely to see at the store, the magnum holds twice as much wine—1.5 liters— as a regular bottle. It is actually preferable for use in aging fine wines because a larger bottle of wine ages more slowly, allowing it to develop a more complex character. A side note, some sparkling wines made via mé́thode champenoise are fermented in magnum-size bottles, whereas the larger, more unwieldy bottles are usually filled with Champagne or sparkling wine that was fermented elsewhere and, as a result, may not be as good. See also Balthazar, Imperial, Jeroboam, Methuselah, Nebuchadnezzar, Rehoboam, and Salmanazar.