Rio Mainstream Striper Fly LineRIOs Mainstream Striper fly lines are made specifically for striped bass and coldwater saltwater anglers. The line taper is a quick loading and easy casting and is suited for a variety of fly sizes from large baitfish imitations to small crab patterns. The lines are intermediate density, sinking at 1. 5 to 2 inches per second, are entirely clear for stealth while fishing, and also include a neat welded loop on the front end for fast rigging.