This is the cheaper of two different styles of cover for Weber 57cm kettle barbecues. It simply drops over the top of the barbecue and provides protection from the elements almost down to ground level. It is made of vinyl and has kept the barbecue clean and dry in spite of some fairly stormy weather and heavy rain.
I had initially decided to not use a cover but I found that rain water managed to get inside the barbecue via the vents in the lid and, as I was storing it under a bat hibernation box, needed something for hygiene reasons as well.
I don't know what the more expensive cover offers as additional protection, but this one seems more than up to the job. The only reason for a four star rating is that nothing is provided to tie the cover onto the barbeque, so it can be prone to lifting in strong winds - it hasn't been totally removed (yet) but I decided to punch two holes in the base so that I could attach the cover to one of the legs `just in case'.