Mercury-class ships are an advanced type of battlestar introduced into the Colonial Fleet sometime after the First Cylon War.
It features full armor plating, 8 engines as opposed to 4, as well as 4, fully operational, flight pods. Allowing the Mercury-class Battlestar to carry a larger number of viper squadrons. Features a perminate flight pod system and is assumed that it does not require to "retract" the flight pods before making a FTL jump. And it's quite larger than the Columbia-class Battlestar
Mercury-class battlestars include the Pegasus and, presumably, the Mercury.