I had a TopGear one on my car . . . for about a month
First off it had to be custom fitted not only to fit round the diff, but also the tail pipes to be aligned and moved back (stuck out about a foot ). Quality was ok, sound was nice from the outside, but on the inside it did my head in. very drony as I did a fair few miles in my zed. I also though the tail pipes were too big and out of proportion
Got a Miltek instead