I bought 2 bottles as I had a badly marked caravan front window.
The product did an amazing job and I have not even used 1 bottle.
The efficacy of this depends on the effort put in. It took a lot of elbow grease but the result is amazing. I have read other reviews that say they used a microfibre cloth rather than the cotton cloth stated on the bottle. I may try this on a couple of deep scratches that I am still working on.