HIS PSMOBIBK Wavemaster MOBI Portable Speaker (Black) Integrated Class-D amplifier for excellent acoustic performance Integrated Li-Ion-battery (USB chargeable) for up to 10 hours playtime Astonishing sound, elegant and stylish design The Wavemaster is an advanced 2.0 stere0 speaker for all non-amplified stereo sources. If offers excellent and powerful audio reproduction combined with a compact and stylish design and superb Pop-in/-out-mechanic: MOBI is small! Pushing upper and lower part together can further reduce its size to fit in any pocket