This USB Host Shield designed to be easily combined with “Mini” variant of Arduino Board, specifically, Sparkfun 3.3V Arduino Pro Mini. It will also work with other 3.3V Arduinos. Also, due to its’ small size it can be used as general MAX3421E breakout board.This shield is fully compatible and supported by USB Host Shield Library. Arduino Pro Mini is not included.USB Hosemini board makes Arduino very easy to communicate with a USB slave device, such as USB keyboard, mouse, U disk, camera, Android phone and so on. Using USB Host Shield with Arduino also allows you to implement Google ADK.It supports 3.3V / 8M / 328 Arduino Pro mini and3.3V FTDI.