A Hammer-Head (sometimes known interchangeably as a HammerHead, a HummerHead or a Hummer-Head) is a UIMS battlecruiser, that is maybe one of the biggest cruisers in history. It is 500 meters long.
In Starblade, it is over 600 meters long has a durability level of 12 and has armor plating. It's weapon is a Missile Launcher.
In Star Ixiom, it is 800 meters long.
In Shattered Stars continuity of the FreeSpace universe, it is 1600 meters long.