About this 3D model

Occasionally having trouble with small tall objects, I decided to make http://www.thingiverse.com/thing:4442 which is adding a fan to cool down small surface layers while printing so the previous layer has sufficiently cooled down not to be pushed way by the material deposited with the next layer... but in the middle of the plastic/paper cutting and taping, I figured it would take me less time to just draw this up and bolt up the little fan (this fan proved very hard to tape to the plasticor paper duct. The STL file is designed for a 40x40mm fan than I obtained from an old broken VGA card. The overhang on the inside of the part is quite significant but I managed to print without major problems without any support material