"I bought two of these because they were a good price and have a 10 year guarantee. The product is well made but basic and this is probably why its so cheap compared with some other makes. my bigest issue is with the installation support. My first problem is with the instructions enclosed with the window, its in pictorial format but crucially the pictures differ from the actual product so getting the orientation correct is a real pain. What really messed me up, is that the instructions have the measurment of the first batton supporting the window wrong, if you follow it and fit a slate flashing it comes up too short, i ignored it and fitted it closer to the bottom edge of my tiles to get it right. My other problem is with the companys web site, the videos do not work!! some are mpeg and some are tlv format (i have no idea why). You are better off going on utube and looking at the Fakro window installation, which is a similar product. I wasted hours getting this window water tight simply because there was a lack of support. So to sum up, the window is good value but a real pain to fit unless you have done one before. Next time I would seriously consider paying more for Fakro or velux."