wtf is this?

[nissanfanatic]

Ive put on headers and an exaust system. factory cat with a touch remains. The only o2 sensor there is the one on the exhaust manifold(header). I have a metal band that goes on the catalytic stud facing the rear of the car where the exhaust system connects. It goes on by means of a washer. It looks identical to the ground strap that goes between the engine and firewall.