Edifier K815 Educational Student Headphone, Sound Pressure Adjustable, Independent External Sound Cards, 120° Adjustable Noise-Cancellation Features: Professionally developed for online education with a 120-degree Adjustable microphone Precisely adjusted sound pressure levels to protect the hearing of children The large black voice coil diaphragm unit delivering outstanding sounds Independent external sound cards for crystal clear communications Shielded wires with the large magnetic rings for less interfered online calls 120° adjustable high-sensitivity noise-cancellation microphones for easier communication Adjustable headbands for comfortable wearing Born for high-class technology and extraordinary sound Specifications: Frequency Response : 20Hz-20KHz Microphone direction : Single point Connecter : USB-A plug Cable Length : 2.8m Impedance : 40Ω Sensitivity : -42dB+/-3dB Sound Pressure Level : 91+/-3dB Inner Carton 190mm x 88mm x 235mm(LxWxH),0.08kg(gross weight)