The four balanced-armature driver design of the W40 will take your listening to an entirely new level. The award-winning sound of the W40 features a beautifully-flat frequency response with articulate lows, precise mid-range, sparkling highs and performance that is perfect for recorded and mastered music. The Westone W40 is the ideal first earphone for those music lovers and critical listeners looking to get the absolute most from their listening experiences. Ideal for all personal audio and video devices. True-fit Technology 60 years of experience designing products for the ear, has resulted in a universal-fit earpiece that is compact, low-profile, lightweight and extremely comfortable. Our proprietary ear tips enhance the performance of the W40 by ensuring a great fit and seal, right out of the box. Balanced-armature Drivers Westone's proprietary balanced-armature drivers provide enhanced sonic detail and frequency range that extends well beyond other in-ear solutions. Westone Bluetooth Cable Full-resolution Bluetooth Cable uses aptX technology to deliver extraordinary detail, clarity and a dynamic soundstage that has to be heard to be appreciated. The Westone Bluetooth Cable features; 8 hours of battery life, a 10 meter/ 32 foot range, has a water and dust resistant IPX-4 rating and features our exclusive MMCX Audio connectors, which allows the Bluetooth Cable to be used with any custom-fit or universal-fit earpieceLess Than