Publisher's blurb: The Tunnel Wye and Passage group of Naked Geomorphs contains 15 tiles, each with a trio and a pair of connected tunnel entrances (T), and rock (R) at the remaining position. Sets A and B are completely interchangeable. I.e., tile T150B can be replaced with tile T150A, without changing the basic structure of your map. Set B has broad, unconstricted passages.