An adaptor/reducer for a 120mm case fan to a 100mm diameter air conditioning duct. Used on my fume cabinet for my RepRap Prusa Mendel. (Short description: http://www.youtube.com/watch?v=YKh6kgO77Us) The A/C ducting is standard 100mm ducting, as used in range hoods and bathroom extraction fans. The fan end is based off a standard 120mm Case Fan aperture and bolt pattern, such as: http://au.element14.com/sunon/kd1212pmb1-6a-gn/fan-standard-120mm-12vdc/dp/9606416Adaptor dimensions: 120mm x 120mm x 100mm high. Mounting Holes: 4.5mm diameter holes, suitable for M4 Fasteners. The holes are counterbored for a M4 washer. (Not shown in my photos)I printed mine with: 0.3mm layer height 2 perimeters 3 solid layers 10% infillFeel free to reduce the layer height, however this will increase the print time, and it's a long print. It has been mounted in a cantilever position with the weight of the ducting hanging off of it for 6 months now, and hasn't had any problems. If you can check your gcode before printing, ensure that the 100mm cylindrical section is printed as a solid wall. I reduced the wall thickness to 1.35mm in this model to allow the wall to be printed in ~3 perimeters. This should reduce the printing time from the original version which printed the inner and outer walls as two concentric walls with a small gap between them.