As you can see I just taped a box fan into the biggest/closest-fitting cardboard box I could find, in my case it's a mini fridge box. I've googled around and haven't seen the idea. I'm moving air out of a 4x4x6 grow tent with three 4 inch ventilation holes. Obviously I would just tape the back closed and cut holes for the ducting then run it into the tent. The fan is 20". Would this work? I'm taking and uploading pictures now.