I don't plug my USB drive directly into the car's armrest port, because the fit is very very tight. And removing it, I feel I might bend connectors on the car. Therefore, my car came with a short 6" USB cable extender. I plug the extender into the car port, and my USB flash drive into the extender. That way I don't risk damaging the connector on the car. Any damage would be on a $2.00 cable.
I use a 8 GB Sandisk Cruzer Micro. For those who want to plug the USB drive direclty into the car and close the armrest lid, the Sandisk Cruzer Micro will work out. But if you have a larger USB flash drive, then you may need to get the extension cable. My M3 came with the cable.