Double-taper lines are ideal for softer-action rods like bamboo and fiberglass. They roll cast beautifully. They're also reversible -- once the front section wears out, you can attach it to the backing and use the other end as the tip. Every Mainstream line undergoes the same rigorous production processes and quality control standards as all RIO fly lines, and is made in RIO's Idaho manufacturing facility. Each line is built with a slick coating on a supple memory-free core, for the best in performance.