The new JVC HA-FX300 employs a range of sound-enhancing technologies, including an aluminum evaporation diaphragm, a new internal dual-metal structure and aluminum housing. The new aluminum evaporation diaphragm used in the HA-FX300 reproduces high-frequency detail more accurately than conventional cellulose or polymer-based diaphragm designs. To further enhance performance, the headphone features JVC's new Bi-Metal structure. The drive unit is housed in a stainless steel base wrapped in a high-specific-gravity brass ring to eliminate vibration and energy loss. Other innovations are aluminum housings, designed to reduce resonance, and the use of OFC (oxygen-free copper) to minimize transmission loss in the 1-meter cord. The HA-FX300 also offers a plug that is compatible with Apple's iPhone. To ensure a snug, comfortable fit, the headphones come with three different sized silicon rubber earpieces and a pair of memory foam earpieces for a customized fit. These provide superior isolation from external sounds and minimize sound leakage.