SEALED 'XW' RING CHAIN RK's XRE series chains are the successor to XSO chains. Compared to XSO, XRE series chains feature a 20% longer wearlife. XRE chains include XW-sealing rings which provide two lubrication pools which help protect against high speed abrasion and prevent dirt and debris from penetrating the inner rollers/bushings of the chain. XRE series chains are available in 428, 520, 525 & 530 pitch. XRE's features create a perfect balance between high tensile strength, lightweight while maximizing wearlife.