Red4Power R4-B004B. System type: 2.0, Recommended usage: mp3 player, Form factor: bag. RMS rated power: 4 W, Frequency range: 275 - 20000 Hz. Connectivity technology: Wired, Interface: 3.5 mm. Power source type: Battery, Battery type: AA. Width: 90 mm, Depth: 180 mm, Height: 65 mm