This has just come off my Phase 1 T4 but might fit others.
It was custom fitted by a powerflow dealer and is all stainless with chrome tips, it has many many years of life in it still.
It gives the car quite a nice low rumble but not so much that it sounds like a tractor and is actually almost as quiet as the factory box until you put your boot down.
Pictured here beside a Jetex box, as you can see it's a fair bit smaller.
The box was welded onto a factory mid section so i cut the box off before the weld to preserve the entire thing all that the new owner would need to do is chop it behind the weld and pull the bits out then cut a slit or two in the pipe and slide it over your existing pipe and clamp it.
Located in Central London but its boxed and can be sent by delivery courier anywhere in the UK at the buyers expense.
I'm asking £100 for it.