BlackHeart Crossbow String - BlackHeart crossbow strings are handcrafted using the right blend of modern materials, machinery and time-honored techniques. Result: crossbow strings featuring the innovative GlideLock servings and exclusive DuraWeave construction that makes for the absolute finest system available today. Each string is meticulously crafted to fit your crossbow. Made to fit Ravin R18 Crossbow. Made in U.S.A.