It is an integral-structured metal coupling with a spiral slit in the round material. A perfect integrated construction eliminates backlash. The A and DS models with high-strength aluminum alloy and 3000 model ( 1441 model) with stainless steel are available. The A model and 3000 ( 1441) models are single-slit models with high flexibility of maximum angular misalignment 5 deg.. And the DS model is a double-slit model with high torsional rigidity. Two fastening methods can be selected for each model, the set screw method and clamp method.