There are also Timeless legs, Timeless cloaks, and many more Timeless items that I haven't found yet, but they're a really interesting gearing item. You'll note, first and foremost, that they are BoA, so they can be posted from character to character. Once they arrive in another character's mailbox, it seems that they detect that character's loot spec, so the specialization you have selected from the drop-down menu on your portrait. Using the item will create an item level 496 soulbound piece of gear that is appropriate to that spec, so you can see from the header image that in this instance it has made a ring that is nice for my elemental spec.
The drop rate of these, on the PTR at least, is relatively high, in about 10 minutes of rare-killing I had amassed two curios and a boot item, all BoA. It's a really good catch-up item, as it can be sent to any alt that needs gearing, and create items specifically tailored to them. In my opinion, at least, Mists of Pandaria really needs better ways to gear alts, particularly tanks who don't benefit from PvP gear, and depending on the drop rate, this might just be one of them!