User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-3062343-20120121010046/@comment-3062343-20120121020203

Yeah, X is G-Rank armour for the regular monster, Z is for the subspecies (they're S and U for High-Rank). From what I've seen, the final upgrades are quite good (for example, the final Jho Lance is probably the best Raw Lance in the game with Sharpness +1 (667 Raw, 150 dragon with Awaken, natural white (purple with S+1), -5% affinity, 1-Slot)), it's just the upgrades before that are pretty poor. It does seem very tough to get it to appear though, I've done plenty (maybe 50-60) of the quests in which it can appear, and I've not seen it once.