A component of a surgical navigation and/or device tracking system (e.g., computer-assisted neurosurgical ultrasound navigation system, surgical microscope equipped with a tracking camera) intended to function as an optical reference to enable spatial tracking of the position/movement of a patient, fiducial marker, and/or surgical instrument (e.g., stereotactic surgery probe, dental drill), and/or to register surgical instrument size. It may be attached to the patient, fiducial marker or surgical instrument, and may contain features (e.g., reflective spheres, contrast patterns) detectable by a tracking camera [e.g., infrared light camera]. This is a reusable device.