Steel couplings have the torsional stiffness to handle servomotors, line shafts, and other equipment, and they help avoid resonance problems in high-speed machines. But they can't handle angular or parallel misalignments. Elastomeric couplings, on the other hand, can cope with misalignments and eliminate corrosion or fretting problems, but don't have the stiffness for some applications. To bridge the gap, Zero-Max, Plymouth, Minn., has developed a CD line of couplings that use an open-arm disc pack made of rugged composites. It lets the couplings handle misalignments -- up to 3° angular, 0.025-in. parallel and 0.160-in. axial for the Single Flex models; and up to 0.89-in. parallel and 0.32-in. axial for Double Flex models -- and are stiffer than elastomeric couplings. CD couplings also resist chemicals and water in hostile environments, a characteristic neither steel nor elastomeric couplings have. Custom composite discs offer a range of stiffness and flexibility combinations to meet specific application needs. Four different hub styles are available, including hubs for standard and over-sized bores, as well as clamp style and quick-disconnect hubs.