Tankless Gas Water Heater recirculating pump question?

[Alan Kish]

I am looking at the Rinnai Tankless gas model RU199in. I cannot tell if it comes with a recirculating pump or not. Does anyone know? Also what exactly does this pump do? This is the Rinnai model that I am looking at. Also I have ICF walls in my basement (foam filled with cement). Could this unit mount to this or do it need wood to mount to? It says the unit is 65lbs.
Thanks in advance.....
https://www.amazon.com/Rinnai-RU199IN-Water-heaters/dp/B07CW426QZ

 

[Fitter30]

External pump