I've bought a pair of these as Amazon has them on sale, they ship from Japan. These IEMs have the best isolation of any IEM at a whopping 42dB, they also have superb audio quality, they have been described as having a very 'accurate' audio quality so if sound accuracy matters to you these are a great choice. Having such great sound isolation means that you can listen to audio at lower volumes potentially preventing damage from happening to your ears.
Side note: I bought these a few days ago and then after they shipped I found this on eBay, one lucky ozbargainer can potentially get these for $128.50AUD on eBay. http://www.ebay.com.au/itm/Etymotic-Hf3-/222451117840?hash=i… I've checked eBay for these IEMs previously to no avail but here they are brand new a fantastic deal. I really should've checked eBay again before I bought them on Amazon, oh well.
That's a bit optimistic :D
Sound isolation is a prerequisite for all IEM's to deliver sound properly at all.