If the o-ring I need matches the diameter of vacuum hose I have, I've used that. And if you need a gasket for your air cleaner to carb, vacuum hose is good to use for that, also. I made one of those around 1980 and I'm still using it today. Just cut so the ends butt together, get about a 3/4" long piece of copper wire that fits in the center, bend that to the right arc and join the two ends as Jerry says...or I've also used rtv to glue them together and a product called GOOP (which is white but works ok).
