Rigid couplings with precision honed bores on straight bore couplings, with bore sizes as small as 3mm, are available in carbon steel, high-grade aluminum for low inertia, and in 303 stainless steel. The couplings are by Marlborough, MA-based Ruland and are used when shaft misalignment is not present or desired, with the rigid coupling often used to help establish the alignment.

Applications include test and measurement systems, imaging, patient positioning, and liquid handling such as chromatography. The couplings are RoHS and REACH compliant.