The package says it all — "An audiophile listening experience for when music matters." You might remember the little blurb I put up a while back concerning the Shure E2c headphones. I replaced those a few days ago with their latest offering, the E3cs. The only reason I even thought about getting rid of the old pair was because they caused me a slight pain in my right ear after prolonged periods of use. Though the headphones came with a fitting kit, my ears were apparently too small for the smallest set of available "sleeves." The E3cs solve this problem by not only providing smaller "flex" sleeves, but by also shipping "ultra-soft" sleeves in addition to the others. The sleeves found on the E3cs are the same as those available for the E5cs — their top-of-the-line cans ($499). You can find reviews of the E3cs here and here.
I should point out that you can purchase the entire line of Shure in-ear products at the InMotion kiosks found at airports. I was unaware of this until a few days ago when I was snooping around some headphone forums trying to get the skinny on the E3cs, which weren't yet shipping from Shure.com (they were supposed to start shipping on the 5th, but it was delayed a week). One of the forum contributors was going on and on about how great these headphones were and everyone else was scratching their head trying to figure out how he got ahold of them so early. He finally spilled the beans and said that he got them at the airport. Upon reading this, I called the InMotion kiosk at the San Jose airport (which is less than five minutes from me), and sure enough, they do carry them. I picked up a pair within the hour.