Etymotic Research ER4S microPro Precision Matched Balanced Armature Driver In-Ear Earphones High performance balanced armature drivers are precision matched to within 1 dB Designed to compensate for the high frequency emphasis in recordings Popular with musicians recording engineers and audiophiles; can be used with a headphone amplifier if desired Braided cables for reduced microphonic effect Includes an assortment of eartips for a comfortable fit and carrying case