Sony XBAZ5 Ultimate Hi-Res In Ear Headphone Hybrid 3-way driver system capable of faithful Hi-Res audio reproduction, 16mm dynamic driver unit with ALCP for rich, deep bass, Newly redesigned full-range Linear Drive armature for clear midrange, Magnesium Super Tweeter armature for silky smooth highs Full, Magnesium housing for reduced vibration and smooth frequency response, Network circuit reduces electrical interference, minimizes vibration, for delicate high-frequency response, Balanced audio capable Beat Response Control for tight bass response, Secure and custom fit with freely adjustable ear hanger, Hybrid Silicone Earbuds, in 4 sizes, provide a precise fit, Foamed Silicone Earbuds, in 3 sizes, provide increased noise attenuation