I received my cast brass exhaust nut from Bob's and I am impressed. I had a nut that came from one of the other suppliers and the new cast nut. I put both on a new manifold I had. There is really no comparison on the fit of the threads and how easy the new cast nut screwed on. Based on the weight of the new nut and the thread "feel", I believe it is going to be a good fix for the continuous nut problems I have had in the past. I hope this takes care of not having to use the after market clamp type nut holders I have had to use in the past. I did not measure the angle of the machined surface that goes against the exhaust pipe, but the new nut has a better matching angle than does the one I had in stock, as far as the angle cut on the manifold does.
I can't provide an opinion as to how it works because I have not installed it yet. But if the looks are any indication, it should work well.
I'm going to wait until Chickasha. I'm sure Bob will have some there, and I'll save the postage.