"I bought three of these for my Velux roof windows and they could not have been easier to fit. I had all three installed in well under half an hour, with just one screwdriver and a pair of scissors. The instructions are all pictures which I do not normally like but they were so clear I have changed my mind as far as Velux is concerned. They may not be the cheapest but I would not now use anything other than genuine Velux. By the way I've also fitted a velux flyscreen to one window - so far - and that was easy too - except for the VERY odd shape of my roof! It's an 1800 French house with a roof that looks like the guy was drunk when he built it! No nice smooth inner plaster boarding, or nice neat rafters, just chestnut boards fixed to knobbly tree trunks. Two more flyscreens to go!"