NFC Function: NFC tap to connect, Support NFC mobile device touch connection, no need to connect manually. Support AUX, 2-RCA(L & R): With AUX and RCA audio port, suitable with various audio devices. Bluetooth 5.0: stable connection, Bluetooth V5.0 chip, ensure that music is streamed to AUX or RCA input speakers, car or home audio system by stereo lossless Bluetooth audio signal. Compatibility: Fit for DVDs, HD hard disk players, TVs, CDs, game consoles, mobile phones, earphones, speakers, etc. HiFi Sound Effect: no delay, heavy bass, Bluetooth analysis chip transmission, stable 15M transmission. Model:BT-21 Bluetooth version:Bluetooth 5.0 Interface: RCA, 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