Shure SE310-K Consumer Headphones

Opinion about sound insulating earphones seems to be incredibly polarised - the Shure SE310s being no exception. However I will say here and now that my personal experience is that these phones are truly amazing and well exceeded my expectations. A natural sound across the range with crisp treble and a solid, natural bass put them in the same league as my home-use Sennheiser HD600s that cost over twice the price of the Shures.
Before buying, though, what needs to be understood is that this type of earphone is a completely different concept to what you may be used to, and that a correct fit in the ear canal is VITAL to getting the best out of them. You should find the right size and shape of adapter amongst the variety that come with the SE310s, but the tinny quality I got with some (that actually felt comfortable) explained to me perfectly why some reviewers think these phones a waste of money (either that or they've been sold a counterfeit). If you do happen to have 'non-standard ears' then Shure actually recommend consulting an audiologist who apparently will make make made-to-measure adapters for you. Do it - you'll notice the difference.
The other advice I'd give is to play around with your player's EQ control to find a setting that compliments the SE310s; the 'flat' response may not always give you the best quality. Adjust to your personal taste in the knowledge that the SE310s can handle as much bass as you can.
Finally, you can use the SE310s on public transport with utter confidence - not only will the insulation block out sound leakage from other, less considerate MP3 player users, but you can rest safe in the knowledge that your own pleasure will not infringe on anyone else; to others around you they are completely silent!