The kmc x9 sl bicycle chain 9 speed features an extra stretch proof hollow pin with weight and chain suck reduction key features doule x bridge shape double x durability compatibility shimano and sram 9 speed drivetrain systems connecting link cl566r reusable cl566 non reusable cl366 slotted link for more information on how to keep your bike running smoothly click here to see pbks expert advice on taking care of your chains and cassettes