The Etymotic Research ER4SR is the new reference standard in-ear monitor for those who demand nothing less than the highest fidelity. The next generation of long revered flagship in-ear earphone, the ER4S, the ER4SR delivers increased accuracy with greater sensitivity. Like its predecessor, the ER4SR channels are matched to within an industry-leading 1dB across all frequencies from 100Hz to 10kHz. The new ER4SR incorporates sleek, anodized and laser-etched aluminum bodies and braided, reinforced 5 ft. detachable cables. The ER4SR is a must have for discerning engineers, audiophiles, and consumers wanting the most accurate in-ear monitor available. Included with every pair of ER4SR earphones is an industry-exclusive channel matching compliance graph signed by the Etymotic engineer who precision matched and custom tuned the balanced-armature drivers. Every pair of ER4SR earphones is assembled and tuned in the United States.Transducers : High performance, balanced armature micro-drivers