The CX 6.00BT is fitted with Bluetooth 4.2 and Qualcomm apt-X to ensure true Sennheiser sound,The CX 6.00BT provides unsurpassed comfort and security: Its around-the-neck cable design minimizes the drag of the angled ergonomic earpieces to ensure that they stay in place,For a personalized fit, it comes with ear adaptors in four sizes (XS, S, M, L),It's six hour battery life with fast charging option via USB that adds two hours charge in just ten minutes, Bluetooth version 4.2,Battery Specification: Lithium-ion polymer