Duct for RepRapPro extruder Wall thickness should be 0.6 through out, and you need to rotate the shroud STL so it lies flat the screw holes should be against the bed UPDATE added better v18 shroud and two new clips v2, this prints with 2 perimeters 30% infill, 3 layers top in bottom UPDATE added v19 chopped down v18 after glass plate clips obstruct fan shroudPrint out and fasten to fan using existing bottow screws (it slides upwards from bottom of the extruder) Clip design included to nip top together if needed Note the bottom fan screw bosses need filing away level to normal screw head depth if you havent already done this Print settings i used layer thickness 0.2mm no support no infill 1 parimeter (my nozzle setting is 0.4mm... buthave 0.5mm) Watsdesign came up at same time as i was creating this, but this is specifically for RepRapPro extruder, also same as him not sure about print quality improvment Update 3/3/2013 added ver 16, dropped duct by 1mm and narrowed the duct exit, getting better cooling now but will have to see if less air flow effects the extruder carrier (although mine was printed in abs)