Metal USB both can be used as USB and hand-ring, more kids, younger adults like it, suitable for business gifts and promotion activities. Can do custom color and personal logo. The product support OS: Win98 / XP / Vista / Mac OS9.X / Mac OS Linux 2.4. Maximum reading speed is about 10M/s, and writing speed is about 7MB/s.521M,1G,2G,4G,8G,16G,32G,64G can supply. Size is 3″ x 4/5″ 1/4″.