One male and one female 120 ohm resistor is essential to terminate each end of the NMEA 2000 backbone. DO NOT use more than one pair of terminators on your network. Use these resistor terminators for proper termination of an NMEA 2000 network to insure your devices can communicate with each other reliably. Thse NMEA 2000 resistor terminators are waterproof and dustproof and designed for use in the marine environment. NMEA 2000 Certified, 100 percent universal and compatible with other manufacturers' products. The NMEA 2000 (N2k) backbone must be terminated at each end wich requires one male and one female 120ohm resistor terminator.