WU-638 USB Flash Disk:Detailed Product Description Features: 1) USB1.1/2.0 compliant, hot plug and play 2) No external power is required, powered by USB bus directly 3) Compatible between different operating systems 4) Electronic storage device, no mechanical components, shake protection, 5) electromagnetic wave protection 6) PC compatible, Mac compatible with USB port 7) optional capacity:16Mb-2GB