The MicroSD card is a very small flash card that is mainly used in mobile phones, but because of its small size and increasing storage capacity, it is now used in GPS devices, portable music players and some storage disks. Its size is 15mm x 11mm x1mm, which is almost equal to the size of the finger. It is a compact flash card. It can also be used in the SD card slot via an SD adapter.
I love it! Works great in my Galaxy Note 8! Fast enough that I can throw pretty much anything at it. If you're wondering, modern Android versions (starting with Lollipop, as I recall) have the ability to read up to 1 TB of external storage. While this 128GB card is the maximum capacity you can currently buy*, the leading manufacturers are feverishly working to make larger capacity cards. For now, though, I think 128GB is enough to handle all the 4K video I can shoot.