This is the controller for the cnc machine which basically allows the machine to interface the computer via the printer port. This was the most fun part of the entire cnc project. I really enjoyed building this. The controller came as a kit from www.hobbycnc.com and was very well put together. The kit had all the parts needed to build it, the motors, cables, connectors, the only things I had to buy seperately were the case, and transformer.