Advance Vent, X-Vent & X-Vent BT helmet systems. The helmet sets come with a comfortable six point harness and ratcheted wheel mechanism that allows for easy size adjustment while wearing. They have NRR 25 hearing protection and an etched spring steel mesh visor. The ADVANCE Vent helmet system (Type 1, Class G) is a vented helmet with a 2200 V electrical rating. The ADVANCE X-VENT & X-VENT BT (Type 1, Class E) are a non-vented helmet with a 20,000 V electrical rating. The helmet systems are CSA & ANSI approved. The X-Vent BT helmet has hearing protection that is Bluetooth compatible (22 NRR rating).