Red4Power R4-B003US USB 2.0. System type: 2.0 system, Recommended usage: PC, Speaker placement: Tabletop/bookshelf. RMS rated power: 4 W, Impedance: 8 Ом, Total Harmonic Distortion (THD): 10 %. Connectivity technology: Wired, Speaker interface type: USB/3.5mm. Current: 0.4 A, DC input voltage: 5 V