Features: Built-in 400mAh rechargeable lithium battery, long lifespan; supports USB (U-disk), TF-card for playback and transfer. Brand new and high quality Built-in digital to analog chip, supports AUX, RCA, USB, TF interfaces. Built-in high-resolution microphone, supports wireless listening to songs, hands-free calls etc. Equipped with a digital LED display with high resolution, work status and Bluetooth mode are clearly visible. Product appearance is exquisite, and the Bluetooth receiver (RX) and transmitter (TX) are integrated in one. Using a Bluetooth 5.0 chip ensures stronger compatibility and stability. Bluetooth version: V5.0 Supported protocols: RX: A2DP AVRC TX: A2DP Working frequency band: 2.402GHz - 2.480GHz Power: Class 2 (Class II) Signal-to-noise ratio: approx 90dB Distortion: less than 0.1% Input: 3.5 mm AUX+RCA+ USB+TF Output: 3.5 mm AUX+RCA Supported formats: MP3/G729/M4A/ALAC/DTS/MIDI/G726 Working current: less than 40mA Built-in battery: 3.7V/400mAh Charging current: approx 500mA Charging time: approx 1 hour Battery life: RX approx 6-8H, TX approx 8H Bluetooth range: approx 10M/3.3ft Charging method: Micro USB 5V/0.5A Supported devices: Android, iOS smartphones and tablets, active speakers and Bluetooth speakers or earphones that support A2DP/protocol connection Product size: approx 70x70x30mm/2.75x2.72x1.18in Note: Color distortion may occur due to different computer resolutions. Size discrepancies may occur due to different computer resolutions. Packaging includes: 1 x Bluetooth adapter 1 x Type-C charging cable 1 x 3.5 mm audio cable 1 x red and white RCA cable 1 x manual