Acoustic Research Hi-def 2.4GHz wireless transmits true audio sound through walls floors and ceilings up to 100' from transmitter. Uncompressed audio for CD quality music and extra voice clarityPatented design: 2 speaker drivers in each earcup. Lighweight padded self-adjusting comfortable headband. Frequency response: 20Hz-30KHz. Li-Polymer battery for extended life up to 12 hours. Digital wireless technology for reliable transmission of music. Small and compact designFast working automatic pair functionTransmitter can be powered by power adapter (included) or 3 AAA batteries (not included)Includes power adapter