This 2.1mm I.D. straight DC power adapter is the exact size for Kantronics TNC's. Also fits Wouxun battery chargers. The O.D. is 5.5mm. Molded with 6 feet of 18 gauge wire and connects to any mating 15/30/45A Powerpole. Fits Kantronics TNC's, Elecraft KX3 and Wouxun battery chargers. Additional Model #'s 78-DC21ST DC21ST UPC: 840128900727