My 85 250r was missing the exhaust flange sealing ring .Iv looked for them couldnt find anything and silicone only last so long.I was given a stock banshee headpipe last year.I didnt know they used o-rings on them till I was cutting it up to use a section for my 84 200x when I noticed the o-ring.I used the o-ring on my stock 85 flange.I had to pry the headpipe on but it doesnt leak.