i just installed a new KMC X9 chain after breaking the Shimano HG chain that was on before. i didnt save that much wait with it (-2g) but boy was i supprised at how well it shifts! i would have got the X9SL but since i plan to get a new group soon and will need a new chain just went with the X9 since it was so much cheaper and will get the X10sl with the new group. its the same chain without the hollow pins and plates. i was shocked how much smoother the chain made shifting, especially up front. its a great upgrade for very little $. the missing link is also nice to have.