DURAGADGET Retractable USB Laptop NumPad Attachment for Lenovo Miix 2 10, Miix 2 11, ThinkPad X1 Carbon 2014 Edition, Flex 14D, IdeaPad Z40, Flex 15D, IdeaPad Z50, IdeaPad Y40, Ideapad Y50, Lenovo B5400 Same size as a normal keypad with full size keys; makes entering numbers a breeze. No external power source necessary. No software required - Plug in and Play with windows. Retractable 65cm USB Cable so your wires won't get twisted and for extra carrying convenience. Comes with a 2 year warranty and our simple no quibble returns policy.