GSM Outdoors GWP-DFM: The pinnacle in electronic shooting muffs, the Firemax is the result of over three decades of experience in industry leading hearing protection development. It incorporates Walker\'s legendary sound activated compression protection built into a slim streamlined design. The digital platform includes four selectable frequency modes controlled by silent soft touch digital buttons and powered by a 2000mAh rechargeable lithium batter for over 200 hrs of performance protection.