Recently I decorated a prayer room at our church, and needed 2 curtain panels for some small windows which were causing an uncomfortable glare in the daytime. There happened to be a Dollar General Store across the street from the church, and since I wasn't looking for anything fancy, I purchased 2 curtain panels for $10.00 each.
They were advertised as light blocking and energy saving, however they didn't really block that much light. I would not recommend them for a bedroom. Also, I was disappointed that there were some flaws in the material, so I guess you get what you pay for.
They are called Thermal Back Panels, and the color is Twilight. I was able to easily install them with a simple extension rod inside the window frame. They did solve the problem of glare, but certainly were not very light blocking. The panels are 40 inches by 84 inches.
Since I was decorating the room with lots of colorful large banners, I did not want the curtains to detract from the banners, so I chose a very neutral color.
They are advertised to keep the room warmer in the winter, and cooler in the summer. The panels are machine washable, and can be tumble dried on the gentle cycle. A warm iron can be used, and they should not be dry cleaned.
All in all, they worked for the room I needed them for, so I am pretty pleased.