Feature:1. NOISE REDUCTION: Noise cancelling headphones have a built in HD microphone that can be twisted at will and comes with a USB sound card to keep your voice clear. Provides clear conversations even in noisy environments.2. EASY TO USE: Telephone headset is easy to use without special operations. Easily turn on and off answering, speaker volume up or down or microphone mute at the touch of a button, for all your daily needs, plug and play.3. ALL DAY COMFORT: Monaural communication headset provides you with an ultra light wearing experience. Soft ear cushions and a flexible headband won't weigh down your ears, ensuring you concentrate on your conversation with long lasting wearing comfort.4. EXTENSIVE COMPATIBILITY: Monaural customer service headphones are compatible with devices with RJ9 headset jacks and can also be used with devices with USB ports. Ideal for home offices, call centers, telemarketing, customer service, teleconferencing, etc.5. ULTRA DURABLE: Monaural customer service headphones are designed with rugged construction and materials that ensure superb performance and make them durable. Long headset cord provides flexibility for mobility.How to Use:Plug and PlaySpecification:Item Type: Phone Service HeadsetProduct Material: ABSModel: H390D-RJ9-U900Color: BlackType: BinauralPlug: RJ9, USB Sound CardFunction: Call, with USB Sound Card, Speaker Volume Up or Down, Microphone MuteScope of Application: Compatible with Devices with RJ9 Headphone Socket, Can Also Be Used for Devices with USB Interface.Speaker Parameters:Sensitivity: 105±3dB (at 178mV 1KHz)Voice Coil Impedance: 150±15Ω (at 1KHz)Frequency Characteristics: 100Hz-10KHzDistortio