Gear couplings are torsionally rigid and are supplied to two designs – completely flexible and flexible/rigid. A completely flexible coupling comprises two hubs with an external gear and two outer sleeves with an internal gear. It's a universal coupling for all sorts of applications and accommodates all possible misalignments. A flexible/rigid coupling comprises one flexible geared half and one rigid half. It does not accommodate parallel displacement of shafts but does accommodate angular misalignment. This type of couplings are primarily used for "floating shaft" applications.