Designed to work with the XX1 crankset, the SRAM PC XX1 HollowPin Chain was designed with narrow and wider inner profiles that fit with the alternating thicknesses of the teeth. This results in a positive connection to the chainring so that it won't slip. Unlike traditional pin style chains that require a tool to fix, the XX1 uses SRAM's PowerLock connecting link. SRAM recommends that the PowerLock Link be only used once so that strength is not compromised. Additional Links are available separately.