It's not waterproof, indoor use only. I agree that it's hardly the most vital accessory ever, but the GTI is not my daily driver and, in the winter especially, it often stays in the garage for weeks at a time accumulating dust (however clean I try to keep the garage

)
I get my covers (this is the 3rd one I've had) from Specialised Car Covers in Bradford. They're expensive, but very high quality and they are available in 8 or so colours, with or without piping.