Tough Tow Ropes, Bridles & Harnesses Line strength is key for tow ropes, bridles and harnesses for tubes and towables. At iboats.com we carry tow lines ranging from 1,500 to 6000 lb. strength ratings. Not only are our tow ropes tough, but also are quality made by manufacturers like Straight line, Kwik Tek, Airhead and SportsStuff, designed to last in even the harshest of marine environments. Shop a variety of 2 section tow ropes for custom adjustments, and a variety of colors for easy organization and identification.