What is this thing?

[thunderclap]

I used to own a PowerMac but last year sold it for a Mac Pro. I was cleaning out my desk drawer today and discovered an extension for the PowerMac but can't for the life of me remember what it's for. I'm pretty sure it's a wireless antenna of some sort, one that doesn't seem to be compatible with the Mac Pro I have.

So what is it? A photo is attached.

 

[JesterJJZ]

Airport antenna. I had one left over too. You can hock on ebay for about 20 bucks.

 

[magid]

It was for the Powermac G5

 

[thunderclap]

Good to know. Thanks!