ER4SR is Etymotic’s new reference standard hi-fidelity earphone, for those who demand nothing less than the highest fidelity. The next generation of our long revered flagship earphone, the ER4S, the ER4SR delivers increased accuracy with greater sound output, or sensitivity. Like its predecessor, the ER4SR channels are matched within an industry-leading 1dB across frequencies from 100Hz to 10 kHz. The new ER4SR incorporates significant cosmetic and functional improvements, from a sleek, anodized and laser-etched aluminum body to the reinforced, user-replaceable detachable cable. The ER4SR is a must have for discerning engineers, audiophiles, and consumers wanting the most accurate in-ear earphone available.