They're sh!te.
I had one on my mk2, the fit was appauling. Sold it to a mate (he knew it was a shoddy fit) and within 3 months the welds were cracked where the pipes enter the silencer. Ashley didn't want to know as i didn't have the original receipt, which i suppose is understandable, but the thing was quite clearly brand new. Anyway, he welded it up a couple of times and ended up chucking it after a year.....