This is just the navigation chip for Humminbird GPS units that covers our book Top Secrets of Lake Fork Volume 2.  This item is for folks that previously bought the book and would like to complete the set by getting the GPS chip built for their Humminbird brand units.  (Book sold separately) (Released 1/20/2020).  This is a companion chip of coordinates that enable you to use the book with your GPS unit better.  It does not contain contours.