The Crane Quad is designed as a 4 filament, color mixing print head. It needs filament in each of it's ports to prevent back flow. This does not mean that you can not use the Crane Quad for single color or single filament prints. Simply adjust your setting appropriately when you slice your model, and make sure your Quad print head is loaded properly in that there is filament in all 4 ports, regardless if you intend to utilize each of them or not.