The beauty of the Shock Cord is that it provides an easier fit than molded rubber- rand skirt varieties - thanks to the forgiving stretch of the bungee cord. You'll also notice a tighter seal as the shock cord tucks under the cockpit rim, and plenty of durability, thanks to 3-mm neoprene and a RimGuard wrap along the edges to thwart abrasion. The Shock Cord is also available in an all-nylon version - great for touring and learning.