“This powered armor appears to be composed entirely of lightweight ceramic composites, rather than the usual combination of metal, and ceramic plates. It seems as though it should give even more protection than the standard, advanced power armor.”— Fallout 2 In-game description
The advanced power armor Mk II is a model of power armor used exclusively by the Enclave military forces, developed after the Great War. Like its older brother, the standard advanced power armor, it's matte black with a menacing appearance, but with a few significant differences - it appears to be composed entirely of lightweight ceramic composites rather than the usual combination of metal and ceramic plates.
This armor, like the standard advanced power armor, works as a disguise when worn around Enclave members.
The armor is five pounds heavier than the standard advanced power armor, which may sound odd, due to it being composed almost entirely of lightweight ceramics. However, it's reasonable to think the additional weight could be from thicker amounts of armor, or additional machinery for increasing Strength by 4.