Elastomer couplings are a type of shaft coupling. They transfer torque between two shafts and perform tasks such as power transmission, compensating alignment errors, but also damping of shocks and vibrations. Elastomer couplings ensure optimal power transmission by using various materials, and also based on their material properties and shape. The properties of the respective elastomer coupling simultaneously prevent vibrations of the drive shaft from being transmitted to the coupled shaft. The following article discusses which properties these are, how the hardness of elastomers is determined and what application examples there are.