Ok so i had a off brand ebay 4 inch carbon filter, the 4 inch ducting fit perfect over it. I just got in my new 4 inch x 12 inch Phresh filter and the ducting will not fit over it. Its slightly larger. I took my old carbon filter and matched u the flangs to the new Phresh filter and the old carbon filter flange and actually slide into the Phresh filters flange. Anyone ever run into this problem? Is seems like it might be a 4 1/2 inch flange :no: