Jaybird's X4 sport earphones combine rugged versatility with great sound. They're sweat and weather-proof, and with a wireless Bluetooth connection, your movement is unencumbered. Long-lasting battery power keeps you going through extended workouts, and secure fit design keeps them comfortably in place. They're ideal headphones for the all-round runner and outdoor athlete. X4 audio The X4 inject crisp, clear and uncompromising audio into your exercise routine. The sound can be tuned to your preference with adjustable EQ in the Jaybird app on your smart phone (available on iOS and Android). Read more… X4 wireless With Bluetooth technology, you can connect to your music without plugging in, just pair them up with your smart device. Charging via USB, the Jaybird X4 keep going for up to 8 hours of playtime. Take hands-free calls with ease with the in-line remote control. X4 tough Fully weatherproof, the X4 are IPX7 rated so you can confidently use them in all outdoor conditions, and they're protected from perspiration. X4 design Sport Fit Plus design can be worn over or under the ear. A selection of ear-tips and three sizes of ear-fins lets you find the perfect fit for comfort, stability and security.