Blackheart Crossbow Cables 21 1/4 in. Parker. Featuring DuraWeave construction process which includes pre-stretching the strands resulting in highly consistent cable length. Each cable is meticulously hand crafted to fit your crossbow.15.1875 for Horton Storm RDX. Package Contents: Blackheart Crossbow Cables BlackHeart crossbow cables are crafted using a blend of modern materials machinery and time-honored techniques. Featuring DuraWeave construction which process includes pre-stretching the strands resulting in highly consistent cable length. Each cable is meticulously hand crafted to fit your crossbow.