Vtin Bluetooth 4.0 Hands-Free Car Kit Car Stereo Adapter Music Receiver with Ground Loop Noise Isolator, 3.5mm Aux Jack, Siri Activation Rotatable Control ! Easy to control and volume up/down,with ergonomically designed knob controller: Just twist the multifunction button to switch to the next or previous songs, or twist and hold it to adjust the volume. (Long press "MFB" about 3-4 seconds to activate Siri.) Noise Cancelling ! Equipped with Advanced Ground Loop Noise Isolator, No More background Humming and Hissing! Enjoy clear sound and music in your car! Dual USB Car Charger: 1A+2.4A ! The 1A port supplies power for the receiver, another USB port (MAX output 2.4A)for charging other devices simultaneously. Hands-free+Voice Dial ! Built-in microphone allows you to talk hands-free. Long Press multifunction button for 3 seconds to use the Voice Dialing function to make calls easy and safe. (PS: Make sure your phone support Voice Dial :) Double Link+Long Transmission! Latest Bluetooth 4.0 technology, supports LONG Transmission Distance(Up to 60 feet) and allows you to connect two Bluetooth-enabled devices at the same time.