Standard USB flash drives, also called thumb drives or jump drives, are available at most large retail stores or electronics stores. It is most beneficial to buy a smaller USB flash drive size (2-4 GB) without any additional software already pre-loaded onto it. The number of books that will fit onto a flash drive depends on the size of the books being downloaded. A 1GB flash drive will hold 96 hours of audio books. Almost any NLS book will be smaller than 256 MB, so you should be able to fit several titles on a 1GB or 2GB flash drive.