Rinnai R65IN Tankless Water heater Questions

[MikiCab]

I am going tankless but this tank looks like it needs a new flue. Rinnai R65IN. I am looking at a 12 inch flue Model: 223181 Non-condensing. I think is correct but the instructions of the tankless water heater is it not that clear that this is the one but there is not that many choices so I am kinda sure this is universal.
Also if any has any experience with this model let me know or have a recommendation for a different model.
Thanks in advance