I don't think its good because its only a normal type, but it is rare in the Pokemon games...
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Porygon 2 and porygon- z
Have a porygon hold upgrade then trade and boom its a porygon 2.
You have to have the up-grade then trade it to evolve into Porygon-2 and then a dubilicius disc for Porygon-2 to evolve into Porygon-Z
Porygon can evolve into Porygon 2, while holding an Upgrade and traded. Even further, Porygon 2 can evolve into Porygon Z, while holding a Dubious Disc and traded.
An Up-Grade is an item that evolves the Pokemon Porygon when Porygon is traded while holding it. Porygon evolves into Porygon 2.