There are several different dual extrusion systems out there today. While dial extruders can be nice to have, they also very commonly introduce new problems into the 3D printing equation. Such problems include scratching and oozing. 3D-Proto thinks that they may have come up with a solution to both of these issues with a new Dual Parking Extrusion system. Basically the system takes the extruder not in use and parks it to the side, returning it back to the build area once it is needed again. This keeps the extruder away from the print while not in use. More details on this new extrusion system can be found here: http://3dprint.com/26590/dual-parking-extruder/