This pipe is intended for holding a rolled cigarette or a small amount of smoking material in its larger end.  The smoker's mouth goes around the smaller end.  Please only use this accessory in legal circumstances and as a novelty only.  The design consists of seven gears ranging from eight gear teeth at the mouth end to fifteen gear teeth at the material end.  The OpenSCAD file is configurable so that you can change the shape and opening sizes any way you wish.  Please note that the value of cp=3 is nearly minimal for passing ShapeWays design requirements.  This affects the number of teeth possible for a desired opening diameter at either end.  If you would like to purchase this pipe from Shapeways you can do so at the following link:  https://www.shapeways.com/model/2995740/gear-pipe.html?li=aeTabs for which I will receive a 10% profit above material cost.  The total cost will be $42.76 if you buy it from my account (at the time of this writing, January 2015).  If you prefer to set up your own account and use the included STL file or another design from the modified OpenSCAD file, then you will save 10% of the cost.  Either way is fine with me!  :)Please note that Shapeways does not list their products as food safe - this product is intended as a collector's item and a novelty only.  Les