I have a vent in my bedroom right in the middle, over my bed, which I never open. Being a late sleeper, it has been a constant irritation to have the morning sun coming through the vent cover and waking me up. So, I found this cushion that is intended as insulation but fits perfectly into the 14" vent opening and blocks out a lot of the light. Works great and sells for $10 at Camping World. (I suppose if I were handier and could bother buying a cushion and covering it with something, I could have gotten it cheaper.)