I bought these shades to use in the bedrooms on a temporary basis, while work was being done on our house. The shades block light well (except for around the edges, where nothing I've found blocks all light) and keep anyone from seeing in, even at night, with the lights on. They were easy to cut and hang. For me, the drawbacks have been that the adhesive does not seem to be quite strong enough and that the shades don't stay down all the way. I've dealt with this by putting a strip of painter's tape across the top to reinforce the adhesive and by using the little clips that are meant to hold the shade open to clip the bottom of the shade to the window sill.

On the plus side, I think that these shades could be left up for a long time if, for example, someone is just moving into a home and doesn't have the budget for more-permanent shades or other window dressing. At less than $5 each when I bought them in a box of 6, these shades seem like a good alternative to nailing up sheets or using some other temporary approach.

This product is what you would/should expect it to be: a lower quality, but much cheaper alternative to expensive higher quality blackout shades or curtains.

Pros: simple design, easy to install, does a great job of blocking light (the pictures speak for themselves)
Cons: low quality, made of paper so it crinkles easily, does not fold back up well once opened/extended

I would definitely recommend these shades though, especially for the price. My only advice: do not install these on windows you plan on opening and closing a lot. As mentioned in my "cons", these do not fold back down well and would be a huge headache if you tried to open and close these often.

Note: as you can see in the pictures, I installed these on the bottom of my existing shades in my daughter's nursery. So when you pull the shades up, the blackout curtains follow. It works pretty slick

Looks nice when first installed, but doesn't last long if you have central air. Sure, it's cheap and it's paper, what can you expect, right? But I think I had realistic expectations. Despite that, the concept just doesn't work if you have a central air or any kind of forced air ventilation system. Installation was quick and easy, and it looked GREAT when first installed in my office. One week later, the results are no longer so pretty. Unfortunately, every time the central air comes on or turns off, the air pressure change in the room causes these to be pushed in towards the window and pulled out from the window. This back and forth motion caused my blinds to look like this after a week (see attached photo). So yes, great concept, could work well in the right environment, but people should be aware of this issue before ordering.

There are some bad reviews for this and honestly, I can't figure out why.

They're inexpensive.
They're a non-permanent solution for someone renting.
They're completely light blocking.
They're easy to use.

I had no trouble installing them at all. I just cleaned the window sills and stuck them up. I did add some staples to the ones in my children's room because they tried to rip them down. (Woo ... Toddlers!!!)

PRO TIP: If you have large windows I recommend trimming the excess off the bottom. I have very large windows and I found out with the ones in my room that because the blinds so big they are too heavy to hold themselves up. The blinds will relax after a few days and straighten out a bit. I trimmed them a little each day for about 3 days until they seemed to stop relaxing. Trimming the excess off the bottom solved the weight issue and I've had no problems since.

Easy to put up QUICKLY. No light coming through! Baby is snoozing as I'm writing this. Cost efficient. I just wish the other side was white (both sides are black). It is not thick enough to insulate, but that is not what it is for. Material feels like butcher paper. Easy to cut and super-sticky adhesive. Clips are included. All of mine were congruent in size, just make sure you pick the right one for your windows.