24 Bit Digital, Dual Frequency (True Stereo) Transmitter and Receiver Up to 9 sets are designed to work together without interference. Operating in the 900MHz range, free of TV broadcast and Wi-Fi interference Rugged, rechargeable all metal body-pack Receiver Will work with most headphones (each receiver Includes IE-9 In-Ear Headphones) Battery: Built-in Lithium Ion 3.7v 1380mAh (quantity 2 per bodypack receiver)