The dryer vent duct size is 4 inches on the Miele. Here are the Miele specs to show you where the vent exits the dryer: T9000

res149, I feel your pain and struggled with this type of thing quite a bit, though I had a smaller space to deal with and was building cabinets for my machines. A couple of questions please. Do you have good access to the area behind the machines when you install? If so, then you have more wiggle room in going for a really tight tolerance. Where does your vent go after the dryer- up, down, through the wall? That is also a factor. Like the man/woman said, dryer vents are typically 4" diameter, but only allowing 4" is very tight. I allowed six and am in good shape, but I think you could get away with 5. Also, there are these rectangular vent attachments which will only need 2" clearance. They have them at Lowes/Home Depot, but this only works if your vent line goes straight down (or maybe up) through the floor.

All in all, I would say you might be too tight for a 31" deep machine no matter what. Like the Miele there are a range of machines that are about 27" deep and that, I think, is what you should look at.

By the way, I have the smaller Miele 1215/1415 and they are about 26 1/2" deep. They are in cabinets I built myself and I can access the dryer vent through a little side door from the other side of the wall. I have an extra 3-4 inches total (26.5 + 6 = 32.5) and this worked out fine for cleaning the vent as needed.

Hope this helps!

I do have access to the area behind the machines because the room is 66.5" wide. The vent goes through the wall to the outside - "L" shape. Somebody else measured the laundry room and that person came up w/ 34" depth - I moved the closet doors more outside within the door frame so that I could gain 1 1/2" - so now we are talking about 35 1/2 ".
Should I try the Whirlpool Duet pair ?