The glass can certainly vary in thickness. We had a customer buy a screen seal for a Morris Minor from us. He complained it didn't seal properly. When we looked at the car, it turned out the screen was only 3mm thick :shock: Apparently had a label on it as made in Taiwan! Can we not make *anything* in the UK anymore?
Of course, there is no guarantee that the 'genuine' one will be any better. Land Rover, like all others will buy from the cheapest source. When was the last time you actually got a Lucas part in a Lucas box? Or a Lockheed part in a Lockheed box? They are all buying from overseas now rather than making the stuff here.