Fiber 104 is the highest shrinkage polyester yarn ever used in sailcloth. The Challenge R&D engineering team conducted a collaborative search with leading fiber manufacturers and textile engineers. The purpose of the search was to find the highest shrinkage, highest tenacity yarn in the world that generated the greatest bias and threadline strength. The search resulted in Fiber 104. The high shrinkage makes the tightest woven fabrics in the world, with the greatest quantity of fiber interlockings. It is much more expensive than the other fibers used in Europe and the United states, and is exclusive to Challenge Sailcloth.