3M is a brand of privacy and anti-glare screens for laptops and desktops. Anti-glare screens reduce the glare from the sun as it filters through any window if you sit in front of a window. Privacy screens stop anyone from seeing what is on your screen when they are at the side of the screen. To be able to see what is on the screen they have to be immediately in front of it, so keeping any information on your laptop safe from prying eyes when you are on the train!