Features: With Aux audio interface, you can upgrade the car or home audio to a Bluetooth-compatible audio, listen to music wirelessly, and enjoy free music. OLED work display screen, simple human-computer interaction operation, the operation is more convenient. 3.5mm audio output interface design, flexible and more versatile. Back clip design, easy to carry. Hands-free call, one-click answering of incoming calls. Built-in 250MA battery, long battery life. This product is an OLED wireless audio receiver. After the mobile phones, computers, PDAs and other digital products are connected to the device, you can enjoy Bluetooth-compatible music or hands-free calls through the device. Specifications: Model No: B31 Oled Bluetooth-compatible 5.0 Receiver Support Protocol : A2DP,AVRCP etc. Working Frequency 2.402GHz -2.480ghz Receiving Sensitivity -90db At 0.1% BER Working Current 30MA (Screen Off) Built-in Battery 250MAh Charging Current About 200MA Charging Time: About 2 Hours Use for Time 10h Bluetooth-compatible Distance 10m (Open Area) Charging Method: Micro Usb 5v Output Connection Mode: 3.5mm Stereo Interface Compatible With Androids, Ios System Mobile Phones And Pad, and Other Audio Equipment With Aux Input Function. Note: Due to the problems of lighting effects and shooting angles, there will be certain tolerances in the product, please understand. Please allow 0-1cm error due to the manual measurment. Package includes: 1x Bluetooth-compatible 5.0 Transceiver 1x Micro Usb Line 1x 3.5mm Audio Cable 1x Operating Instructions