Here are two of the ribs side by side. You notice that one has the flanges pointing to the right, and the other has them pointing to the left. The six flanges on the left side of the horizontal stabilizer are supposed to point to the right and vice versa on the other end. Unfortunately, the kit included 8 right ribs and 4 left ribs, so time to call Heidi...at the New GlaStar factory who runs the shipping department. I think I'm going to get to know Heidi well before this process is over.