If you use the USB port in the car, the garmin mount will block the port. The plastic mount has a cutout for the standard power 4 pin and it also slides in and helps keep it secure. Between the lock on the mount and the plug, my 76csx has never bounced out on my snowmobile or truck. Bought the power cord (coiled!) on ebay, works great and also has a led power indicator and fuse on the plug.