What type of hose is this?

View attachment 31502

It's off my TM coming from the heat exchanger. It looks like a common plumbing part to me, but I can't find anything with that thread depth, it looks like 3/4 diameter on the thread size. There's also no data on the hose so I'm not sure what PSI/heat range I need.

Can anyone tell me what it's called, where to get that from and if there's a better one I can use instead?

Thanks!