Ultimate Ears UE900 carrying case. This is a gloss-black case with a very nice hinged lid and magnetic closure. So far, I'm very happy with this case, and haven't had any accidental openings in my backpack.
In this photo, the lid is open showing the spare eartip holders, and the 1/4" plug adapter (which also has a holder to keep it in place). Also shown is the drawstring pouch that holds a bunch of other ear tips.