NFC Function: NFC tap to connect, Support NFC mobile device touch connection, no need to connect manually. Support AUX, 2-(L & R): With AUX and audio port, suitable with audio devices. Bluetooth 5.0: stable connection, Bluetooth V5.0 chip, that music is streamed to AUX or input speakers, car or home audio system by stereo lossless Bluetooth audio signal. Compatibility: Fit for , HD hard disk players, , CDs, game consoles, mobile phones, earphones, speakers, etc. HiFi Sound Effect: no delay, heavy , Bluetooth analysis chip transmission, stable 15M transmission. Model:BT-21 Bluetooth version:Bluetooth 5.0 Interface: , AUX Connection range: 15m Battery capacity: 200mAh Working time: receive 8h/transmit 5h Frequency response range: 10Hz-20HKz Signal-to-noise ratio: less than 110dB Size Chart:60x60x18mm/2.36x2.36x0.71inch Color:Black Material:ABS Package Contents: 1 * Audio Adapter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.