This is a board that's very similar to other Pololu-based electronics implementations, including RAMPS, but it can support up to 5 steppers (three for X, Y, Z, one for an extruder and one for any other function). You can add as many stepper driver carriers as youneed. It is designed to run at higher voltages than 12 Volts, This allows you to put 90 Watts out of one MOSFET and run your stepper motors with more torque and higher maximum speeds. This board is also used on the Mantis-30 milling machine from Protospace and on various Mendel's that people have built.