The F would be equal to a 5500 JD if they made one, it is larger than the 4400 yet smaller than the 6600 all the way through the machine and in the field will run off and hide from the 4400 with a 4 row corn head or 13 ft table and will give a 6600 a good run for their money. I had one but I did like my M2 a little better, it made the 6620's look like wimps!