Gray Ghost Amphibian Underwater Headphones (for Minelab CTX 3030) User-selectable impedance for compatibility with all water detectors. Heavy-duty polymer muffs with full-ear surround, soft comfortable cushions. Special sound-blocking muff design eliminating environmental ambient noise up to 24 decibels. Backed by a limited lifetime warranty. Frequency response: 200 - 3200 Hz... only what your detector uses.