The "O" ring chains actually have a rubber "O" ring surrounding the pin in between the side plates. I keeps the lube in the rollers so relubing is not necessary as frequently, but makes the overall chain width greater. Depending upon the chain you select (if you go the o-ring route) check to make sure you have enough clearance between the front sprocket and the engine case. Do a search here on it, you will find several threads on this topic.
