Publisher's blurb: The Cavern-Tunnel Wye (small cavern) group of Naked Geomorphs contains 27 tiles, each with three connected openings, one or two of which are two-position openings (CD) and the remainder tunnel openings (T). Sets A and B are completely interchangeable. I.e., tile M31A can be replaced with tile M31B, without changing the basic structure of your map. Set A has sections of narrow, one-hex wide, passages, although some of the restricted sections are short (just a few hexes).