SYLLABLE Bluetooth Earbuds, Syllable Wireless Sports Headsets Sweatproof Portable Stereo Headphones with Microphone (Black) Comfortable: The headphones are designed fit perfectly for ears, 3 couple of earbuds for replacement, suitable for sports, music enjoying, and phone call function with mic. 1 year warranty is provided for Syllable D900S Bluetooth headphones. Please don't hesitate to contact us if you have any questions or problems! Compatible: Upgraded aerial and Bluetooth V4.1 with 30ft Bluetooth distance. Work with smartphones, tablets and other Bluetooth devices. (Note: The Left earphone can only be pairing with the Right, could not be connected with Bluetooth device.) Audio Quality: The Syllable Bluetooth headphones are made of active noise cancelling technology, for super bass and 3D stereo sound. Large Power Capacity: The battery capacity is lasting for 4-5 hours. The storage box offers 5 times full charged to the two headphones. Also please note that if there is charging issue, you need to put both earphone into the charging station box. If put only one earbud into the charging box, it will not charge.