Audio quality is our top priority: Experience great sound with a 7 millimeter dynamic driver and a wide range of Bluetooth codec support Long battery life (20 hours) and comfortable wearing: Get up to 20 hours of music playtime with one charge - The ergonomic design​ offers optimal comfort and secure fit with 4 ear adapter sizes​​ Personalize to your everday needs: Fully adaptable controls for music, calls and voice assistant​ - Built-in audio equalizer​ adapts the sound to your personal preferences Full digital control with our app: Our Smart Control app for iOS / Android​ allows all of the earphone functionalities to be modified to your personal choice Enjoy outstanding sound quality no matter your mobile device or your surroundings with our wide range of audio codec support including AAC, aptX, SBC and passive Noise Cancelling Sennheiser uses decades of expertise to drive the world of audio technology forward with every product - for new, unique sound experiences Included components: CX 400BT True Wireless, Charging case, USB-C charging cable, Silicone ear adapter sets (in size XS/S/M/L)