The Original Gray Ghost is designed for the demanding professional coin, relic, and jewelry hunter. These phones are built by detector people for detector people. The Grey Ghost also has a built in large signal blocker to limit the volume of the response to a large target. Heavy-duty polymer muffs with full-ear 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.