Sony MDR-F1 Full-Open-Air Headphones with Impedance Compensator (Discontinued by Manufacturer) Full-open, dynamic headphones with wide stereo soundstage Impedance compensator eliminates variations of sound quality caused by amp impedance differences 50 mm diameter driver for delivery of deep bass and wide frequency range Leatherette headband and earpad material is soft and comfortable Magnesium alloy frame and super duralumin headband