What is the name of this silverlight control?

[BinBin]

I found a nice website, http://maps.spokanecounty.org/
On the top right corner, when you click "tools", a window will popup.
Anyone could tell me what is this control? I do not think it is childwindow or popup.
Or I have to create my own .dll for this.
Or in SL, is there any control like floating panel?
Thanks

[dotMorten_esri]

That looks like a 3rd party control based on the Popup control.