Your curiosity is correct. I now have a streak on my B pillars because of this seamI'm curious if the water actually transfers from the rear gutter to the front gutter. First thing I picture is water coming out where the two gutters meet - No matter how well/straight they were installed. It looks like the water test in the video shows it being poured just on the front section.
Edit: There should almost be a very thin rubber/plastic piece to join the two here. Thin enough that water could easily transfer over it, but strong enough that it won't break.
Sponsored
