For the Bluebird Chain, Odyssey took the proven and reliable KMC 510-HX chain and added a permanently attached, factory installed half-link to one end. When the chain is trimmed to size you can easily decide whether or not to use the half-link. Original factory assembled pin joints are radically stronger than workshop assembled ones, so this is a huge benefit. Industrial grade 1/2" x 1 Half-link and standard Master link included | Odyssey | Bluebird Bmx Chain | Black | 1/8