The Sena Technologies Rider Link (SRL2) is a sleek and low profile communication system tailored specifically to the Shoei GT-Air II helmet. Discreetly placed within the helmet instead of being attached to the side like other devices. The SRL2 operates with a simple 3 button functionality, to allow easy navigation through the commands and settings. If that's not enough Sena Technologies has a smart app that can be downloaded to you phone for an even easier way to adjust your device.; ; Pairs up to 8 Riders Up to 1 Mile/1.6 Kilometer Range (With Clear Sight) 10hr Talk Time Noise Cancellation: Advanced Noise Control GPS Navigation (When Paired with GPS from ether your bike or Phone) Built in FM radio Battery charging time: 2.5 hours Bluetooth 4.1