I think(?)this might be a little inaccurate? I have a airport extreme and bought a airport express to extend/enhance my wifi in my house. There were "dead zones" in my house, so I bought this a put it at the opposite end of my house from where my extreme is and now I have perfect signal strength everywhere. ...Hopefully its not my imagination that the airport expressed fixed this
***EDIT: I also just checked my settings on my routers via Airport Utilities and my Airport Extreme says "Create a wireless network" and my Airport Express says "Extended a wireless network"*** Hopefully I'm not wrong with all of this