Targeted to the overall needs of the average fly fisher. RIO s Mainstream series of fly lines have been developed to meet the overall needs of the average and novice fly fisher and are designed to optimize rod performance with slightly heavier and shorter head lengths. 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. Slightly heavier than standard lines for easy loading Supple core with a slick cold water coating.