Large O ring on dizzy? Rubber or other

Great info guys. So right now I have a big thick (hardened) Oring which presses up against the hold down strap. Then on the shaft there is a groove, and in that groove sits a very thin oring, much thinner than the groove itself. I have never seen colored O rings at the Auto store, just the black ones. I have never seen any oil on the Large O ring, nor have I ever seen any oil leak from the distrib.