Sentry HW702 Wireless Headphones with Transmitter, Two-Pack (Discontinued by Manufacturer) Great for iPhone, iPod, MP3, CD, DVD players, and home, office or outdoors; built-in FM radio Two headphones and transmitter; reception up to 100 feet Frequency range 20Hz-20kHz; Impedance: 16 Ohms; Sensitivity: 110db 4 foot cord length with 3.5mm plug Transmitter uses two AAA batteries (not included); Headphones uses four AAA batteries (not included)