From the Wizards of the Coast website:
Illustrated cardstock terrain tiles for use with the Dungeons & Dragons Roleplaying Game.
This D&D Roleplaying Game accessory designed for use with the Dark Sun Campaign Setting and the Marauders of the Dune Sea adventure gives Dungeon Masters an easy and inexpensive way to include great-looking terrain in their games. This set provides ready-to-use, configurable tiles and three-dimensional enhancements with which to build exciting encounter locations.
This accessory contains six double-sided sheets of illustrated, die-cut terrain tiles printed on heavy cardstock, allowing you to create desert oases, sandstone vaults, and other dungeon and wilderness fixtures. Some of the tiles can be combined to create 3D terrain elements. It is ideal for Dark Sun campaign adventures or any other D&D setting.
This product will be released June 15, 2010