BlackHeart Horton Storm RDX & Ten Point Nitro RDX Crossbow String - 40.875in - BlackHeart crossbow strings are crafted using the right blend of modern materials, machinery and time-honored techniques. These bowstrings feature GlideLock center serving which enhances durability, reduces friction, reduces serving separation and almost eliminates the ridges between the serving strands. The DuraWeave process includes pre-stretching the strands resulting in highly consistent string length. Glidelock center-serving Duraweave Pre-stretched For Storm RDX Crossbow Models