All the advantages of the H51, plus exclusive noise-cancelling technology which reduces transmission of ambient noise from the workplace. Noise-cancelling microphone limits background noise Supports Call Clarity and patented SoundGuard Plus technologies for superior sound Adjustable headband provides an ultra-stable fit Soft ear cushion for comfort Lightweight- only 1.8 oz/51g 10' coil cord with Quick DisconnectTM option Flexible microphone boom Adjustable clothing clip H51N: Supra NC Monaural Headset Supra H51N H51 Headset Express Headset Monaural Loracomm Plantronics H51N: Supra NC Monaural Headset