Slave cylinder seal to metal hardline on N54?

[CamN54]

What’s up everyone. So here’s the story…first off I’m an experienced tech (for the most part) and just got done installing new 335is clutch, solid rear subframe bushings, poly diff bushings, new tie rods and a couple other odds and ends. What a project! Took me 11 days on and off. All buttoned up now but I made a rookie mistake. I reinstalled the slave cylinder at an angle and when I went to go try the clutch, it blew apart the slave cylinder as has happened to many others.

No worries, purchased a new OEM unit from rock auto, got here this afternoon. Installed it just as the old one was, but I was getting a nasty leak where the hardline attaches into the slave with the plastic sleeve/metal clip thing. So I removed the slave and hardline to take a look. It appears that there should be an o-ring/seal that will sit down in the slave feed hole and seal around the metal hard line. (Keep in mind, this is a plastic slave cylinder, so it doesn’t use a standard threaded fitting)

Am I on the right track here? I was pissed when I broke the original slave cylinder and threw it away, now realizing it probably has the little little seal that I need

I have tons of o rings here at the shop but nothing fit. Looks like it needs to be really thick and have small ID and OD. REALOEM shows no sort of seal, newTIS shows nothing about the seal, parts guy at my local dealer said I was wrong and it should be a metal hardline that threads in…whatever. If anyone has run into this issue please let me know! It seems like it should’ve came with the new seal. Maybe it fell out?

Thanks for your help
-Cam