Initially, I bought one roll, just in case it turned out to be a dud. I got a special membrane spatula for €7 and a spray bottle for €3. I put soapy water inside and started! It's better to cut the pieces beforehand; your job will be much easier. Spray the glass generously. Remove the protective film and place the material without fear since it floats on the soapy water. Once it's in place, wet the membrane and remove the water with the spatula.

The process is a breeze if you're even a little handy. When I finished, I ordered two more rolls. Unfortunately, it seems it doesn't have good transparency (which is justified for its price), and I don't know if the appearance will improve as it dries. I installed them yesterday. However, this doesn't bother me because I used them on the staircase windows, so I don't care. On the other hand, the performance is more than excellent. The staircase used to be an oven, now it's just fine! Time will tell about its durability. It's good to clean it with a spatula and soapy water, though.

I'm coming back after a week. Since I had some material left and had joined two pieces from the first roll to make it fit, I decided to remove it and put on a new one. Even though it had been stuck for a week and baked by the sun, it came off immediately, proving that it doesn't really stick (probably never does). Others have mentioned this in their comments. I assumed they didn't know how to install it. So, be careful when cleaning it.