Ok. I have tried every product on the market. I was obsessive about this. Let me save you a lot of trouble and tell you the best blackout product on the market - tinfoil. Wet your window, cut to shape, it sticks up. Anything else you buy will let light around the edges. Foil always works, it's cheap and it travels well. Just use foil. A good quality one and some cheaper flimsy ones have little speckle holes in them.