This Back up and zip line arm is held together by the maillon rapide. It is recommended for long zip lines (longer than 100m). Two back up arms are required per zipline and while assembling, the wire rope must be maintained with 1 ferrule "h" per back up. Made for a 7x19 12mm or 1/2" wire rope or a 6x7 12mm lang forming in case of heavy traffic.