Bulge was one of OZ's space fortresses, it was by far the largest mobile space vehicle in the After Colony timeline. At 8 kilometers in length it was more than twice the length of the space battleship Libra. Bulge was likely large enough to be considered a space colony not only due to its size but also due to its similar shape and appearance. The massive, disc-shaped gravity block generates artificial gravity, and an agricultural plant allows the fortress to become self-sufficient.

Its primary purpose was to serve as OZ's command center in space. The large beam cannons were perfect for assaults to destroy other large objects such as space fortresses and colonies, and they were capable of producing their own spacecraft, mobile suits, and weaponry - enough that it was capable of defending itself from a much more technologically advanced foe, as well as the Gundams - by deploying sheer numbers of its own mobile suits. When the Bulge cannon was constructed and added to the fortress's limited arsenal, its power in space became much more dangerous - enough that it became the final stronghold of OZ before its eventual demise.