OK here's the difference…
There are actually several different types of “O”-ring style chains. O-rings are perfectly round and technically are considered OLD technology. The newer styles are called X-rings. They are usually in the shapes of X's or W's. This is because the X-shape creates lubrication pools which helps make your chain last longer. X-ring chains last about ten times longer than an O-ring chain.
Roller chains are mostly called Heavy Duty chains and typically don't have o-rings. Most SX bikes use Heavy Duty Non-O-ring chains. However once you start riding outdoors etc you should be running an O-ring type chain.
The type of chain you get on the bike depends on what kind of bike it is. Forexample a CRF250R comes with a Heavy-duty NON-O-ring chain. A CRF250X bike comes with an O-ring type chain… Comprende?
If you race you should be running a heavy duty SX chain. If you want something that lasts you should run an O-ring, RX-Ring, Ultra-Ring, XW-Ring.
Hope that helps ya.
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