Can somebody tell me what this is, please?

[0rinoco]

This was in one of the USB ports on my iMac when I bought it, last year. Any idea. what it is? It's 3/4 inch in length.

I

 

[Longkeg]

Plug it back in. Unplug all other USB devices. Run a system report: Apple Menu-> About This Mac-> System Report. On the left click USB. A list of currently used USB devices will come up. Figure out and note which one is your mystery gizmo and Google it. It’s a dongle of some sort. Could be Bluetooth or some other network bell or whistle. Could even be proprietary for some app.

 

[0rinoco]

Thanks. I'll do that.

 

[arn]

yep, reminds me of a bluetooth dongle for a mouse

 

[0rinoco]

Thanks to all. Looks like it is for a mouse.

 

[Fishrrman]

It could be a radio receiver for a mouse or other USB peripheral.

It also could be a USB-based wifi adapter, but those are usually marked.

Or, bluetooth adapter as Longkeg mentioned above.
Good idea he suggested about running a check using "about this mac".

You could also try this: