The HD387 in-ear headphones feature an 8mm drive unit that produces a wide, flat frequency curve and provides full range detail. The delicate treble is matched with a powerful bass, giving an immersive music experience, The three-dimensional rear cavity design provides the effect of earphones such as speaker guiding holes, which makes the low frequency more solid and clean. The ergonomic removable earloop design is firm and comfortable, suitable for sports wear.