The item works well and in my view should include the ND filter. The foil as is was to bright to take flats that were long enough to prevent shutter shadow on my Atik 383 ccd used on my SV80S refractor. So I purchased the ND filter. Once installed in the foil the RGB flats were excellent but the NB filters Ha, OIII and SII requiered extremely long exposures, 480 seconds for a SII flat field. I had to remove the filter and use white sheets of paper in front of the foil and no filter for Ha, OIII and SII flats. RGB flats were achieved by keeping the ND filter in front of the flat field foil and white sheets of paper. Perhaps Gerd Neumann could design a sleeve to place in front of the foil, this would expedite the adding and removing of the filter. It took some additional engineering on my part but I was able to produce good flats for all my ccd filters. The foil does generate a superb flat field that is even across the entire field. If you have a fast system be aware of some issues using this product but the resulting flats are excellent.