The Redster has a unique shell story-carbon-fiber strands co-injected with molten polyurethane into key power-transmission zones of the lower boot and the spine, with a grooved sole designed to flex slightly. That makes for a powerful but light boot with a balanced and sensitive feel, testers said. Its fit is tailored to an aggressive, technical skier whose foot has always been too wide for narrow performance boots. "Great contact and feel." Notes: Carbon fiber shards are co-injected into the polyurethane shell at key power areas but the new "kerfed" boot sole profile allows for underfoot flex and better snow feel. Flex Chassis bootboards (3 stiffnesses: stiff, medim, soft) allow for customized snow feel.