Do I need o-rings for new heater hose connectors?

[08HoeCD]

I'm going to replace my original tee-style heater hose connectors tomorrow AM in my 2008 Tahoe LT. I just got them and peeked down the large throat opening and see no o-rings. I could have sworn I read or saw that this connector uses/includes an o-ring.
Do I need to buy o-rings separately or are o-rings unneeded for this fitting as it joins to the heater core?

 

[Jagsta]

Is this the one by the firewall? I had to replace the fitting that goes over/slides on to the tee and the o-ring was in that fitting. There was actual multiple o-rings on the replacement connector and I had to remove one of them from aftermarket to make it slide all the way on (there were 3 or 4 bunched up in the fitting).