Geeetech Double Extrusion Head Dual-head Extruder for 3mm filament 3D Printer Reprap Prusa Mendel MakerBot,Hot End V2.0,hotend Dual Extruder. 3 optional Nozzle Size: 0.35mm Nozzle, 0.4mm Nozzle, 0.5mm Nozzle (0.35mm Nozzle) A dual head extruder is a preffered choice if you wish to make multi-colored 3D prints. If you wish to make product prototypes or models with extra detail then multi-colored prints do give many objects, therefore a dual head extruder would be the prefered option. The dual head extruder just gives you that extra possibility of creating prints with more detail than if you were to use a single head extruder.