This means that it may be more efficient to directly build a higher tier mass extractor. It should be noted it is just as expensive to upgrade an extractor, than to directly build one of a higher tier level.

An extractor surrounded 4 mass storages produces an extra 50% mass. Mass extractor production can also be boosted by placing mass storages around them for an adjacency bonus. Higher tier engineers can build higher tier extractors directly without having to upgrade them, which is useful at T3 because the price for an upgrade and the price for a direct build is identical, but when direct building the wreck is left behind and effectively provides 900 reclaimable bonus mass. Initially, T1 engineers and un-upgraded ACUs can only build T1 extractors, but the extractors can upgrade themselves to higher tech levels without need for advanced construction units. Mass extractors can be built by engineers and command units.