I have two details map preloaded SD card from Magellan for the Explorist series 400, 500, and 600. Thought I was having a problem with the detail map when it was a problem with my unit.(Explorist 500) Magellan sent me a free one to check to see which it was. Tried the new map and the same problem, and then I exchanged my unit at Bass Pro Thursday and now both maps work just fine. Now I have two. I would like to offer the extra one out for $50.00 before I decide to ebay it. Please PM if you want it.