Product review (4 stars): the "test fitter" was pretty much wedged beside the dryer with one screw driver ...
We installed this yesterday in about 20 minutes - mostly because we erred on the side of caution when snipping sections off.  It was clearly a 2-man (woman, in our case) job.  One sat beside the dryer to measure and "test fit" while the other was the "mover of the dryer".  Once we had tested, snipped (using tin-snips), tested, snipped, tested, snipped, moved the dryer into position for a final test fit.  Then, we used the aluminum tape to tape the seams (as others recommended).  After that, we put our taped-up vent onto the back of the dryer and used only the ring to secure it. (It fit snug and there really was no room for aluminum tape.)  Finally, we carefully slid the dryer (with vent attached) onto the wall vent.  We used aluminum tape around the seam before sliding the ring around the two pieces and screwing it tight.  At this point, the "test fitter" was pretty much wedged beside the dryer with one screw driver to hold the clamp into place and another screwdriver to secure it, but...success.  Now, here is why it gets 4 stars.  After all that, I am not sure we gained much space.  I wish we'd have measured before we started, but we definitely are not 2 1/2 inches from the wall (as indicated in the description).  More like 4 - 5 inches total.  I think we may have gained 2 inches, but I think it is worth it - especially when you are talking about walking space in a pass through laundry room that leads into the garage and is utilized frequently. I will update if things change as we just finished the install last night.  Also to note, this was put on a brand new Whirlpool Cabrio and the wall vents were professionally cleaned (of all debris and lint) prior to installation.