First, a bit of clarification. In case you didn't realize it, Etymotic has four versions of its ER-4 MicroPro series earphones, each of which retails for $299. We're not going to overwhelm you with all the details of each model, but Etymotic say the ER-4PT, which delivers excellent sound with very accurate tonal balance, is made for "the professional traveler who uses his or her earphones on planes as well as professionally."
The first thing you'll notice about these Etymotics is that the earphones themselves are somewhat long, slender cylinders that make you feel as if you're almost jamming sticks in your ears, which is not a bad thing in this case. Several Etymotic models are shaped this way, and we only point it out from an aesthetic standpoint that these guys protrude from your ears a little more than some earphones.
They come with a two different "Accu-fit" noise-isolating eartips (foam and silicone rubber) designed to completely seal your ear off from the outside world. You can also get personalized "Custom-fit" eartips, which Etymotic offers for $100 extra.
Overall, the ER-4PT earphones are well-designed, with a thick main headphone cord that splits off into two braid-reinforced cables going to each earphone. (The ER-4PT's have a two-year warranty.) One complaint: the plastic surrounding the right-angle headphone plug is on the thick side and if you have a case on your smartphone or portable audio device (say, an iPod Touch), you may not be able to get the plug all the way into your device's audio jack (this reviewer couldn't plug into his iPhone without removing its case).
Read the full review to find out just why they sound as good as they do.