Publisher's blurb: The Cavern Basic and Tunnel Passage (large cavern) group of Naked Geomorphs contains 12 tiles, each with three openings, one of which is an unconnected three-or-more position opening (CSD, CSSD, etc.) and the other two are a pair of connected tunnel openings (T). Sets A and B are completely interchangeable. I.e., tile M94A can be replaced with tile M94B, without changing the basic structure of your map. Set B has broad, unrestricted passages.