Audio-Technica ATH-M50x Professional Monitor Headphones + Fiio A1 Headphone Amp Proprietary 45 mm large-aperture drivers with neodymium magnet systems Closed-back cushioned earcup design creates an outstanding seal for maximum isolation Collapsible design ideal for easy portability and convenient storage Exceptional audio quality for professional monitoring and mixing Bundle includes Audio Technica ATH-M50X Headphones and Fiio A1 Headphone Amplifier