The Collar Power Bank is a 2850mAh battery designed specifically for the Vuzix smart glasses. Ten times the battery capacity of Blade for 10 hours of run time under normal operation. The battery is worn around the neck to comfortably and conveniently extend the run time of the glasses. It also provides pass-through audio from the Vuzix Blade Model 447 to headphones. Note: Vuzix Blade Model 494 cannot use the pass-through audio.