SAC is a special electronic circuitry that will compress gun shots and other loud noises down to a safe level, without completely shutting the noise off. This allows you to hear range commands or communicate with your hunting partners, even when shots are being fired around you. Walkers New Digital Razor in ATACS Ghost camo design. The Digital Razor Electronic Earmuffs are designed with a new ergonomic head band design for comfort and support. Features – Advanced Digital Circuit – Active Dynamic Sound Suppression – Hi Gain Omni Directional Mics – Lighting Fast Reaction Time Wind Noise Reduction – Auto Shut Off at 2/4/6 Hours – NRR 23 d – B(2) AA Batteries.