From the publisher's website:
GameMastery Map Pack: Mines contains 18 full-color 5 x 8-inch map tiles, stunningly crafted by cartographer Jason Engle, that combine to form a variety of mine-themed locales destined to strike it rich!
Customizable Mine Tracks
For use with all tabletop roleplaying and miniatures games and suitable for experienced GMs and novices alike, this product fits perfectly into any Game Master’s arsenal.
Wet, dry, and permanent markers erase from the tiles!