Designed for use with a 50mmx15mm blower fan. This duct covers all of the front area of the sheetmetal ventilation holes that cover the board and lines up with all of the OEM mounting holes provided, no drilling required.This cooler is a work in progress and is meant to use a 24V blower fan connecting to the J20 Jack ( Marked: Fan 19-24v ) port on the UM2's control board. I will update this design once some additional testing has been accomplished.