This is the amazing USB drive named as Flashbag.It was designed by russian designer Dima Komissarov.This USB flash drive changes its size depending on the amount of its data.So, when this device about to blow up sure it is full fill with data.You will see the error message "There is no enough free space" when the device is about to blow up.When you swithched off the flashbag remains pumped up,so you can be easily known with your naked eye how much more data(pics,ebooks,music and other personal data) can be transfered into it.