Plantronics H31CD Starset Headset for Controllers & Dispatch Plantronics H31CD is a modified version of the StarSet H31 headset. The H31C/D boost the incoming audio to make listening easier in noisy environments. This H31CD (43674-01) is recommended for dispatch operators, aviation controllers, military, stock exchange, airport, large call centers. Plantronics Starset Features: Receiver Impedance (ohms, at 1 kHz):600 150 Source Drive Impedance (ohms):600 1kHz sensitivity (dBPa/V, 4 dB): 20.5 Ideal for noisy environments, featuring a complete 6-Size eartip kit. Ideal for those who need a comfortable, convenient headset for noisy environments. The ultra-lightweight, StarSet headset rests comfortably behind the ear. Its soft, pliable VersaTip eartip gently conforms to the natural contours of your ear while providing the acoustic seal necessary to block out background noise. Includes: 1 H31CD Headset, 1 06448-01 Eartip Kit (6 Sizes), 1 17593-01 Claer Voicetube, 1 40700-01 Eyeglass Adapter Kit, 1 User manual, 1 Cloth Storage pouch.