These curtains do a good job at the black out feature.  However, the material is silky, making them seem a bit cheap.  (I probably should have read more about the material)  Also, the way that they attach is with one continuous opening in the fabric, it's a bit tight so it is hard to open and close them.  I probably wouldn't buy them again but they are doing the job. 

Pros: they do black out the light
Cons: fabric, method of attachment to curtain rods