First off, I took a measurement of the foam piece that I took out and cut the coupler about 1/4" taller. I ended up having to take off a little more when I installed it but that's better than cutting it too short. I also had to make the diameter smaller so I cut a piece out of the side. It should be tight fitting but not so tight that you can't easily slip it on. The hose clamps will take up the slack. Next –––>