Sonic 2015 Square Calendar 30x30cm Superb Sound Quality: Plays crystal clear audio without a hitch. Built-in Microphone with CVC 6.0 noise cancellation allows for high quality and clear voice, even in noisy environments like inside a gym or jogging on the road. Advanced Technology: Integrated Bluetooth 4.1 CSR chip allows for easy pairing with smartphones, tablets and other bluetooth enabled devices. Long Battery Life: The built-in polymer lithium battery allows seamless enjoyment of music for up to 6 hours and 100 hours stand-by with a quick charge of only 1.5 hours. Sweat Proof: IPX7 water resistant material prevents headphone damage when you are getting drenched in sweat after a grueling workout. Lifetime Guarantee: We back up each order with a complete lifetime money back guarantee to ensure your total satisfaction.