Before you remove/unplug your USB Flash Drive make sure no data is being transferred to or from the USB.
PCs running Windows XP and above and Macs with OS 9 and above have a "safely remove USB" option that we recommend you follow:
Locate and left click on the "Safely Remove" icon on the System Tray to display the USB devices connected on your PC/notebook. Select the computer drive letter assigned to your USB and click on the "close/unplug" option, so you can safely remove it.
Apple Mac OS 9 and above
Locate the USB drive icon on the desktop and drag it onto the Apple Trash can (icon).