Abstract: A coupling comprises: a pair of hubs including a first hub and a second hub, each having an inner end surface and a plurality of claws located on the inner end surface at intervals in a circumferential direction and projecting in an axial direction of the hub, the inner end surfaces of the first and second hubs being opposed to each other, each of the claws of the first hub being located in the gap between two adjacent claws of the second hub and each of the claws of the second hub being located in the gap between two adjacent claws of the first hub; and a rubber spacer located between the opposed inner end surfaces. A product of a damping ratio and a square root of a dynamic torsional spring constant of the coupling is 1.3 to 12.0.