2 inch antenna, for Dogtra models: 175NCP, 200 series, 280 series, 300 series, ARC, Surestim M Plus, 7000 series, 1100NC, 1200 series, 1500 series, 1600 series, 1700 series, Surestim H Plus, 1900 series, 2300 series, 7100 Series, RRD TX, RRS TX, and RR Deluxe TX.