FFR Heater - "O" ring question

[Gumball]

I'm hooking-up my FFR heater and have a question that I hope some of you can help with regarding the elbow pipes that attach to the heater core inlet / outlet stubs. The kit included two small green "O" rings that appear to go over the ends of the aluminum elbows before attaching them to the heater core stubs - is this correct? They do seem a bit small and like they'd be something that could crimp and cause a leak, but I don't see any other purpose for them based on the parts in the kit.

[Gumball]

Did a bit more research and answered my own question. The Vintage Air website has instructions for their universal cable operated system and I found this:

"Install heater fittings with "O" rings (lubricated) to heater core"

Here's a link in case anyone else needs instructions or wants to see the diagram that goes with this: http://www.vintageair.com/DownloadsSection/Heater%20Systems/50616-VUZ%20Bi-Level%20Heater%20(Inet).pdf