Thunderbird 900 Oil Filter Small O Ring, Where Does It Go

Changing oil and filter on my tbird 900 (1999 model) I have all the stuff ready, however looking in the Triumph service manual and the Haynes workshop manual, it is unclear to me where the new small 'o' ring should fit, even on the exploded views it is unclear to me. I though originally it fitted on the top of the fixing bolt, but that has no groove for it. Am I missing something, pictures would be appreciated, or a clear explanation?
Thanks in anticipation.

Ahhhh! Just discovered where it goes, (I feel such a Pratt) I do hate exploded views, I find them more complicated than their worth sometimes.
Hope the attached photo is of help to anyone else who may be asking the same question.

 

Well its done, new oil filter, new magnetic racing sump drain plug and 4ltrs of castrol power 1 oil. Drive Chain adjusted.
As yet, no oil leaks, drained off 4 ltrs of old oil, removed old filter, left over night to drain out. Put 4ltrs back in, will run tomorrow to check for leaks or any other problems.
I have noticed, that with the correct amount of oil in from standing for a while, and on centre stand, the oil level is covering all of the sight glass?
Should I have put less than the recommended quantity in, so it is half way up sight glass or stick to the factory spec for this bike, maybe when it's run and oil is passed through the system it may level out, but somehow doubt it?

 

Yes will do tomorrow, when I run it. Thanks

 

Higher than halfway, in fact pretty much as it was before, I know there is only 4ltrs in there and that's what is supposed to be in, so I will leave it.
As there is no sign of leaks (touch wood) I am not going to try draining of a smidge, don't want to open a can of worms?
Bike seems to be running well, gear selection seems smoother, it was a little lumpy before, and occasionally missed a selection, but fine now.
Also adjusted the chain, which maybe psychologically makes it seem a smoother power transfer.