Product review (5 stars): Fits requirement
This is exactly what I should have bought in the first place. I went for 2-3 sturdy aluminium options from Home D and Lowes and none was fitting the dryer. I read a review in amazon and ordered it. This is slightly bigger than 4" and hence was a perfect fit to the ducts. This one comes with 2 spring clamps so no need to buy anything additional.