BlackHeart Parker Crossbow String - 35.5in - 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. Each string is meticulously hand crafted to fit your crossbow. GlideLock center serving DuraWeave Pre-stretched For Cyclone (Express, Extreme, HP), Tornado 165, HP) Crossbow Models