Also as you can notice the metal is differently manufactured. See the blueish shades it has? Maybe a cryogenic(maybe i am using wrong word here, sorry) process???
Mine now has turned deep purple like ti exhausts, the same colour as my cat from same company. And smells nicely when hot, strange metal smell!

Team I don't know what the diameter is, I will ask and will post again.

 

stainless steel heat tints at certain temperatures, eventually it will turn dark gray if you run a lot of WOT