Abstract: The dual-purpose adapter for inspecting circular (plug-type or receptacle-type) ruggedized fiber optic connector has a guide and a fitting tip. The guide is formed by fastening a template inserter to a frame in two alternative opposite directions. The template inserter has light channels corresponding in relative positions to the endfaces in the ruggedized connector, and two locating holes for coupling and aligning with the ruggedized connector through two guide pins. Depending upon the direction in which the template inserter is fastened to the frame, the fitting tip may be inserted into a respective end of the light channels to allow the optical axis of an inspector probe connected to it to intersect at right angle with PC or APC endfaces for inspection by the inspector probe. For receptacle-type connectors, the guide further includes the two guide pins which can be locked from axial movement at two positions.