Klein Tools Cat No AESEM1S Earmuffs are engineered to incorporate both Situational Awareness and Bluetooth technologies for connectivity to surroundings and music. The dual-knob design featuring unique grooves for easy identification enables users to precisely adjust their Situational Awareness or Bluetooth volumes. Ergonomically designed vented headband provides cool comfort for all-day wear. These earmuffs charge in 2 hours, providing 25 hours of runtime