Dry Erase Dungeon Tiles: Greystone Square Booster Pack

Dry Erase Dungeon Tiles: Greystone Square Booster Pack - Rules of Play says:

R4I has taken the realistic visual effects even further by implementing a “hidden grid” by rendering a floor of varied size and shape stone tiles, yet still leaving a subtle representation of the traditional 1″ grid. Compatible with both dry-erase and wet-erase markers. More flexible than a traditional battle mat, start your game with a single tile and connect the tiles as the adventurers explore new areas. Never again give away clues as to which way the corridors may lead due to starting placement on a large mat. The interlocking tile modularity allows the Dungeon Master to draw many details of an area at his seat and then simply hand the tile to the nearest player to connect.