The Walkers Ultimate Power Muff Quads are protective electronic headphones designed for use in noisy environments (think range time). The Sound Activated Compression circuit reaction time is 0.02 seconds and safeguards your hearing from loud sounds. Adjustable Frequency Tuning (AFT) feature allows you to customize the unit's frequency response; so you can tune your earmuffs to the frequency that best matches your hearing for crystal clear sound.