Summary This fan duct will allow you to upgrade your cooling fan easily to a 12V DC 50mm Blow Radial Cooling Fan. https://www.amazon.com/Connector-Cooling-Blower-50mmx15mm-uxcell/dp/B00MJU6JR2/ref=sr_1_fkmr0_1?s=pc&ie=UTF8&qid=1476920027&sr=1-1-fkmr0&keywords=2V+DC+50mm+Blow+Radial+Cooling+Fan The fan duct is to be mounted around the original cooling duct of the Wanhao Duplicator i3 using the screws form the original fan. A M4x20 screw (or longer) is used to hold the new fan in. PID HEAT MANAGER- use for best hotend performance This describes how to make your Duplicator i3 use PID heat management for best temperature control of the hotend, no matter which cooler you use. https://www.youtube.com/watch?v=ki-JOwre82Y Edit 11/13/16 Added a fan duct to upgrade from a 40mm fan.