I used this UGREEN card copier to make an operating system copy of my Rpi micro computer. I liked the one usb3 port feature in conjunction with the ability to copy from one micro sd card to another micro sd card.Linux users normally have at least an acquaintance with using the command line editor to identify device files so, I have added the following instructions in case some guidance is needed.If you use the original instillation OS card as your daily OS it begins to fill up with bookmarks, downloads, documents, etc. and, you run the risk of loosing everything if your system crashes. It is best to make a back-up for future use. Rpi tells you how to do this in their SD Card copy prgm (listed under preferences), open and press it’s Help button. It will tell you how make one copy of itself on a micro SD card while the Rpi is running. After you have made your OS copy, put your original instillation card in a safe place. Use your new OS copy as your daily OS card . Over time it will begin to fill up and you want a back-up copy of all your latest files in case of a crash. I use a flash drive to make daily copies of files in case my system goes by by, but, that does not include new software prgms not included with the original os. The system may not allow you to make a copy of your copied daily OS card while your Rpi is running (like it did the first time you made a copy using the original os). I have in the past used two usb3 ports on the Rpi but, I came across this UGreen product which, perked my curiosity with it’s embedded chip requiring only one Rpi usb3 port and , it’s price point was acceptable for a test.UGeen card copier has a regular SD Card slot ,(titled SD) ,and a Micro SD Card slot, (titled TF) , ( I have no current need for the other two slots), and, uses only one usb3 port. The SD Card carriers normally have a manual switch which when turned on to lock will write protect your daily Micro OS card when inserted into it’s carrier. Reference photo (Ugreen_0)The doing procedure:1 Remove your daily Micro SD card from the under side of your Rpi and insert it into the SD carrier and make sure it is write protect locked. Your daily Micro OS card is now protected from any mistakes you may make.2 insert your original Rpi OS card (the one you put away) into the micro card holder located under your Rpi board.3 Have your target micro SD card ready, (the one you want to copy too). It could be a new one or an old one for recycling.4 make sure the two usb3 ports on your Rpi are empty. I assume the other two standard usb ports are used for one keyboard and one mouse.5 plug your UGreen card copier into your Rpi usb3 port.6 Turn on your Rpi.7 When loaded: Bring up the command line editor: at the prompt type in pushd /dev (space between d and /), press enter. This will take you to the device directory.8 At the device directory prompt type in df -khT (space between f and -), then press enter . Study the device list . Reference photo (RpiUgreen_1) attached. Note there is only one sda listed, which is my kingston flash drive which, I should have removed.9 insert your source SD card carrier, write protected, with it’s micro daily os into the large SD card slot of your Ugreen card copier. Your file manager should come up and you can look at the card contents which won’t be empty. Close the file manager.10 in your command line editor prompt :type in df -khT press enter.The updated device list will come up and look for a three alpha codes like: sd(x) (it will have a third letter and sometimes followed by a number). You should also see the card size which may be a bit smaller than stated and the volume used. If you used a 32Gb it may show a lower number. See attached photo. Once you find the three letters write them down.11 insert your target Micro SD card into the small Ugreen slot (they title the slot ‘TF).Again your file manager may come up but the card should be empty if your are not overwriting a card. Close the file manager.12 Go to your command line terminal prompt and key in df /khT and press enter. Reference photo (RpiUGreen_2.)The updated device window will appear: look for another sd(x) code in the device list : you should now have at least two of them with different third letter characters. One should be the same as what you have recorded and the new one which will have a different third alpha character . Write down the new SD(alpha) code on paper. You may leave the terminal open if you wish. Reference photo attached.13 open your Rpi4 prgm list then open the accessories sub list and select :SD Card Copier: see photo above. Select the drop down menu and then select the ‘Copy From Device’ window. In the drop down list find the code that matches your source card code that you wrote down, click on it and check to make sure the correct code is displayed. Remember to have locked your source card for read only.14 Next: open the ‘Copy To Device ’ entry drop down menu and find the code that matches your target micro SD card. Click on it and make sure it is correctly displayed in the window. Reference photo (RpiUgreen_3)15 click the start button. The SD Card copier will let you know if its not going to work. This may happen if you have not changed to your instillation OS card. Naturally you would have to start over again if you forgot to insert the original OS micro card. If it is working and after a while stops or does not appear to be doing anything for about 30 minutes then press the stop button, it may just close ‘hopefully,’ just bring up the SD copy prgm again ,(you don’t have to turn off your Rpi): you may have to reenter your file codes (you don’t have to close your Rpi). I have had to restart from one to three times, in creating a backup. It tends to lose its brains at times and needs to take a break. On restarting it will remember where it stopped and continue even if you turn it off and on but, don’t change the devices.Note: If at any time your Rpi freezes and you have no control from the mouse or keyboard then press any key from f1 to f6 and, (it is supposed to safely shut down the system without destroying your micro OS card).Your UGreen kept with your back-up cards and notes: in a small box makes a nice little back up / maintenance kit. Make sure you keep notes as the next time you have to use it as you may have forgotten the procedure.“ Remember that this is a learning / hobby single board credit card sized computer and, not a main line full featured machine”.