This is 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. You can choose an included or even a mounted Arduino Pro Mini..
So it looks if an Arduino Pro Mini (not included) will be placed on the USB Host Mini