rubber washer for pressurized cleaning canister

[Gaelic]

Do you need an O ring for the pressurized cleaning canister to where it connects to the kegerator itself? I have leakage if I don't use one but doesn't seem to flow very well when I do have one. Can you suggest a certain size if so, if not can you tell me what I may be doing wrong?
Thanks,

[KillianBoy]

Gaelic,
If this one 261707.png.jpeg no not really, where exactly are you putting washer and/or where leaks, which coupler and model of can, please.
KB