Blackheart Rail Lube and Wax Combo Pack. Created exclusively for crossbow strings BlackHeart's premium string wax not only protects your string and cables from natural weathering effects it also deeply penetrates the string fibers conditioning them. UV impervious. Applies clear. 1oz. tube. BlackHeart's premium rail lube creates a slippery surface for your string to glide across vastly improving shot consistency. Reduces center serving wear. Idea viscosity for application. Increased velocity. Scent-free formula. 0.5 oz bottle. Package Contents: Blackheart Rail Lube and Wax An all-in-one craft bowstring care kit. Created exclusively for crossbow strings BlackHearts premium string wax not only protects your string and cables from natural weathering effects it also deeply penetrates the string fibers conditioning them. UV impervious. Applies clear. 1oz. tube. BlackHearts premium rail lube creates a slippery surface for your string to glide across vastly improving shot consistency. Reduces center serving wear. Idea viscosity for application. Increased velocity. Scent-free formula. 0.5 oz bottle.