These are Amazing. Block light,  yes they do. My house is painted and decorated in cool colors,  so these are just what I needed. The length was even great. Fast shipping !!! I'm waiting on my other two sets to be delivered today. I took a picture. I have six hanging now and two more to hang with the 6 today when they get here. I ordered the 52 W and 84 L. My windows are big. They are great.i took one picture with lights on and one with lights off. I highly recommend these.