Purchased these black out curtains for front bedroom(2) dormers that had starlight,moonlight, sunlight and street light streaming through them at all hours of the day and night. When I had a house full of guest coming, I ordered and put up this shade and it blocked all light at night and about 90% of East/South sunlight exposure during the day. I would highly recommend these to all night shift workers like myself because after 30 years of sleepless days, I can finally get a good days rest. I purchased the black out curtains and they provide a 90% decrease in room light. I've since put a valance over the window and have to use a room light or flash light during the day to see it's that dark. I am a 30 year night shift veteran.....Buy them!!! Buy them in the darkest color available (Ihave navy blue and black) and get a good night sleep.