MOTU MIDI Express 128 USB Interface - Open Box MIDI connectivity - Provides eight independent MIDI inputs and outputs for a total of 128 MIDI channels. Expansion - MOTU MIDI interfaces grow with you. Expansion is simple. Add additional MIDI ports by plugging in another MOTU MIDI interface. Compatibility - Works with your favorite software. Includes drivers for Mac OS X and Windows. High-speed USB connection. USB-Powered - Bus-powered from USB connection. No additional power necessary. Rack mountable - With rack ears attached, fits standard 19 inch (48.26 cm) rack at 1U high. Excluding rack ears, chassis dimensions are 19  7  1.75 inches (48.26  17.78  4.45 cm).