97 Metro 1.3 Downstream O2 sensor

What size wrench removes this sensor (near converter) (rear sensor)?...any special hints ? or will ot come out without a fight?
Thanks,
FGlass

Of the top of my head I'm thinking it's a 7/8 and they can be a sob to get out. When you do I suggest you get some anti-seize and give it a good coating.