Air Pump Inline Filter Question???

[sumfishowner]

Hey guys...I'm a long time reader...first time poster. I have a question... I bought a new pump for my aquarium (20-40 gallon air pump), its an Aqua Culture that I bought at Wal-Mart. Anyways...in the box with the pump there were what seemed to be two "Inline Air Filters".....? if there is such a thing.

Anyways... the inlet of the supposed "inline filter" connects to the side coming from the pump, and the outlet connects to the line going into the tank. Does anyone have any idea as to what they are for or their purpose, because the aeration if installed or not installed into the line seems to not be any different?

 

[reg2k2]

Possibly a check valve. Purpose is to prevent water from siphoning back into the pump in the event of a power outtage.