That is the one i see most of the time
Zurn uses metal crimp rings. Wirsbo uses PEX rings as shown in the supplied picture.
But again, at least Zurn only requires that on a gas water heater. Let’s go dig around for a Wirsbo Design Guide…maybe they require it on both. That will make things interesting.
Well, a look at the Uponor (Wirsbo) website didn’t help much. I did see a reminder there that the UPC says “604.11. 2 — PEX tubing cannot be
installed in the first 18 inches of tubing connected to a water heater” and doesn’t seem to distinguish between gas and electric like Zurn does.