Nugget Busters were designed for the demanding professional electronic prospector and gold nugget hunter. If you're just getting started in gold hunting, we're sure you'll never want to use anything but Nugget Busters! surround, stay-soft, non-hardening cushions. Adjustable padded headband... no screws, no wire frame, no rust!. Special sound-blocking muff design eliminating environmental ambient noise up to 24 decibels. Frequency response: 200 - 3200 Hz... only what your detector uses. Sensitivity: 72 dB @ 1kHz min. Impedance: 150 ohms nominal. Backed by a limited lifetime warranty.