This pack of double-sided dry-erase Graystone Dungeon Tiles include 16 5" and 5 10" interlocking square tiles with a 1" grid. Made out of heavy duty chipboard, they're over 1/8" thick and compatible with dry-erase, wet-erase, and liquid chalk markers. This set of tiles provides more flexibility than a traditional battlemat by allowing you to assemble your dungeon map like a puzzle as your adventure grows! The interlocking feature of these tiles makes them fully compatible with our other sets of 5" and 10" tiles for the best dungeon mapping. Use the large tiles for multiple rooms and great halls. Use the small tiles for the connecting halls and corridors.