The SMART HJC 21B is the 2nd Generation Standard Bluetooth Communication System model that supports 21B compatible HJC helmets, with structural interfaces that users can easily mount on HJC helmets. Based on the BT 5.1 low power system, the 21B offers Bluetooth 4-way intercom functionality, with over 22 hours of talk time. The enhanced sound provides users with an HD speaker, to enrich mid-to low-pitched sounds.