1. It can be connected to an external 3.5mm AUX cable (included) for use as a wired headphone, suitable for smartphones, laptops, desktop computers, etc. Frequency range: 50 - 108 MHz. This FM digital radio headphone has a built - in microphone, with super - strong reception sensitivity and a stable and clear signal. Whether you are at home or running, walking, or cycling outdoors, you can clearly listen to FM music and news. It is powered by a built - in rechargeable lithium battery (650mAh) and can work for up to 24 hours. 2. Specifications: - Material: ABS - Dimensions: Approximately 4.75 x 4.75 inches - Battery capacity: 650mAh - Range: FM 50 - 108MHz - Operating voltage: DC 3V, AAA 1.5V x 2 - Frequency range: 50 - 108MHz - Quiescent current: 100uA - Frequency response: 200Hz - 20000Hz - Maximum power: 3.2mw 3. Note: Due to manual measurement, a 1 - 2cm error is allowed. Please make sure you don't mind before placing an order. Due to differences in different monitors, the pictures may not reflect the actual color of the item. 4. Package includes: 1 x FM radio headphone, 1 x 3.5mm cable.