When position accuracy is critical in a rotary coupling application, the high torsional stiffness of a bellows coupling is likely to be required. Additionally bellows couplings flex very easily, minimizing bearing loading, and allowing for smooth operation of the mechanical system. Bellows couplings also have a very low mass moment of inertia, allowing for rapid acceleration. They are the ideal servo coupling when their size and cost are acceptable.

Elastomer jaw couplings, often called spider couplings, offer zero backlash as the result of a specially designed preloaded elastomer insert. Torsional wind-up is slightly higher in these precision spider couplings, but there is no permanent loss of position. Elastomer jaw couplings typically resist shaft misalignment beyond a certain point, and are more robust under slight parallel offset. These couplings will transmit a slightly higher restoring load onto shaft bearings than bellows couplings, but are suitable in most applications where shafts are within a few thousands of an inch of one another. Higher shaft misalignment will accelerate wear in the easily replaceable spider. These jaw couplings also enjoy a high level of torque density and a relatively low cost.