Unopened pair of Etymotic ER4SR in-ear headphones.

From the manufacturer's site:
"ER4SR is the highest-performing single driver in-ear monitor. The IEM shells are made of anodized aluminum, CNC machined with extremely tight tolerances. Using a single Balanced Armature (BA) driver allows for extremely accurate IEM without the added complexity of crossovers, and helps keep the aluminum body small and slim. The included high-quality user-replaceable cable is reinforced and twisted, to improve longevity and durability. Etymotic IEMs are world renowned for their class-leading passive isolation, providing 35-42 dB attenuation (depending on eartips used and the depth of insertion). For comparison, most custom IEMs provide approx. 25-28dB attenuation and foam ear plugs attenuate up to 32 dB. The ER4SR is a must-have for discerning sound engineers, audiophiles, and consumers wanting the most accurate in-ear monitors available."