Several things are possible here: - It has a PSU with active PFC which doesn't care where you plug it in, it'll work on 110V and 220V AC without intervention on your part. - It has a PSU with a voltage switch on the back, which lets you choose between 110V and 220V AC. If it's set to 220V and you're in a 110V AC area of the world, just flip that switch to the correct setting. - It has a PSU with passive PFC which may only work on 220V AC. That happens when buying stuff on the European market.
some of the more expensive ones (Seasonic) just automatically switch when plugged in
Just to be extra clear, that feature is called active PFC, and it's not exclusive to Seasonic or expensive units.
In any case, it's undoubtedly a good deal for $50 if nothing is wrong with it.
-What is best in life? -To crush your enemies, see them driven before you, and to hear the lamentation of the women.