The Walker's Razor Slim Low Profile Electronic Earmuffs feature a Noise Reduction Rating (NRR) of 21 dB, and utilized sound activated compression (SAC) of 0.02 seconds. 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. Your hearing cannot be replaced, so make sure you pick up a set of Walker's Razor Electronic Earmuffs for your next trip to the woods or range. Features Rechargeable (USB charging cable included) Volume Control Knob 300 mAH (40 hours battery life) USB charging port Full dynamic range HD Speakers for clear and balanced sound Sound activated compression Sound dampening composite housing 3.5mm audio jack Rubber spray 21 NRR Black and FDE Models Low noise/Frequency tuned for natural sound clarify Non-adjustable headband