I used it to make a tempory pick shield for my guitar until I could get scratch guard.

Seems to block light well, but very difficult to pull backing from and temperature must be just right to make it stick. Likes to curl from the corner.

(1)Don't be defrauded by the instructions that this product requires just 1 person to apply properly.
(2)This product doesn't use any adhesives and so it won't eventually peel off like regular wallpaper, which will fall off after several years of solar exposure.
(3)Use a very small spray bottle to mist-spray slightly soapy water before applying. The slightly soapy water will (a)help this product to stick a little better to the window glass, (b)allow this product to be moved around and adjusted better after application, (c)make it easier to get rid of the air bubbles with a 12-inch ruler, and (d)make it less tragic if this product accidentally gets stuck to itself.
(4)The seller uses a clear plastic tape that is very difficult to remove and leaves unwanted tape adhesive on this black product after tape removal.
(5)The clear plastic backing film, which eventually needs to be thrown away, is very difficult to remove, especially at the very start of the removal process. I used masking tape on both sides to start the separation process.
(6)Remember that the shiny, reflective side of the black film is the side that must be applied to the window glass. Remember that the dull, rough-textured side of the black film is the side that must never touch the window glass.
(7)Remember that perfection is not possible and that many air bubbles and wrinkles will occur. However, this won't really matter much.
CONCLUSION:
I'm glad I bought this window film product. Even though my Dell Latitude laptop comes supplied with an anti-glare screen that the Dell Inspiron laptop and most other brands of laptops cannot have, I still benefit greatly from blocking out the sunshine near my laptop.

WONDERFULLLLLLL! Just make sure you actually measure and cut lol I didn't... and I stuck it on kinda sloppy and some light through those tiny little cm areas reflects quite a bit! So if you want pure darkness, measure and cut perfectly. ;) I suggest the bigger role for normal bedroom windows- the smaller one I ordered first and had to cut it up, multiple sections to cover my whole window. The larger size works perfectly though. Easy stick on- just use a little water and stick it on! Brush out air bubbles with squeegee or credit card... done. :)

This is a good window cover if you want complete privacy. It is a solid black, not the one way mirror style. Since this is a pretty dark solid cover I bought it to use on a small window, it might look odd used in main windows or big windows. I used a vinyl scraper tool to apply it.