These Mirror Rage are outstanding cleaners. We have a 5 by 3 foot mirror above our bathroom sinks that is constantly getting water spots, yes I am messy. No matter what we used or how we did it there were always streaks. Our water is real nasty and even with a softener it makes spots and forms a hard crud wherever it sets and dries. My wife used these towels with just water and it worked beautifully. I used it on a mirror above our bar sink with just tap water and it worked just as well. They claim these are good for 100 washings but we will probably wear them out before that. Cannot wait to use on our windows.