Killer Concepts Rocksteady Portable Bluetooth Speaker (XS V1.0) - Matte Black Loud and Clear - The developers of the Rock steady XS listened to customers who wanted a portable Bluetooth speaker that was loud enough to handle almost any situation, yet clear enough to play distortion free at higher volumes Lithium Ion Battery - The Rock steady XS uses a high quality Lithium Ion battery, giving you over 10 hours of continuous play USB Port for MP3 Playback or Device Charging with the USB port - You can either connect a USB thumb-drive to play MP3 files or connect the supplied micro-USB charging cable to charge your external device Built-In Speakerphone with a High Quality Built-in Microphone - You can now use your Rock steady XS as a portable speakerphone Connect 2 devices simultaneously. Bluetooth memory for up to 4 devices