Environmental Noise Cancellation: GCBIG workout headphones built-in 2 mics and it work together to reject noises around you, keeping your voice sounding clear for every call to precisely for hands-free calls and Speak-to-Chat detection. ENC noise cancelling earbuds can make others hear your voice very clearly while phone calls. Bluetooth 5.3 and One-Step Pairing: True wireless earbuds advanced bluetooth 5.3 technology. You are getting 2x faster transmission speed and more stable connectivity without signal loss. When you open the charging case, they'll automatically connect to the paired previous device, the range can reach up to 50ft away. When you put it back, the bluetooth audifonos shut down and are recharging.