Publisher's blurb: The Tunnel Wye group of Naked Geomorphs contains 13 tiles, each with three connected tunnel entrances (T), and rock (R) at the remaining three positions. There are actually ten different interconnection patterns; this group contains two tiles for each pattern where all three tunnel positions are adjacent, because those are so useful as edge and corner tiles. Sets A and B are completely interchangeable. I.e., tile T137B can be replaced with tile T137A, without changing the basic structure of your map. Set B has broader tunnels than set A, with no one-hex-wide constrictions in the main passages and an occasional narrow deadend branch.