Roof Vent Cushion or Solar Cover

Previous posts and threads have addressed roof vent covers, but not roof vent cushions or solar covers. Both are intended to keep light out and provide some insulation benefit. They are currently on sale at Camping World (special internet price) and have good product reviews. However, since our TM is currently garaged and I can't remember the exact design of the roof vents (how recessed, screen location, etc.), I was wondering if anyone has used either of these products and if you encountered any problems or have any comments (both products seem to do about the same thing).
Thanks for any feedback.