I did a house today that has had new windows fitted and were cleaned by hand by some sort of chemical by the fitters,anyway on the first clean they came up spotless and the water i noticed ran straight off the glass almost straight away.I`ve heard some people call this glass hydrophobic due to the water not clinging to the glass,by the look of the results it`s almost worth getting this product they use on first cleans after windows being fitted because if all the glass i used WFP on were like this it would make it even easier.