Used genuine BMW exhaust backbox from my modified 2017 BMW M140i.
Great clean condition.
This box is marginally noisier  than the standard box as it has been modified prior to my ownership and really sounds awesome at full throttle.
It comes with the two exhaust tips pictured.
The backbox would be a great addition to other modified parts in the system.

Your old backbox would have the exhaust pipe cut off carefully and this direct replacement would have to be welded (as per factory spec).