These charts are great. A huge step up from paper NOAA charts, they withstand rain and spray. I collect charts for harbors most visited, especially for waters where the boat lives. They will last for years and take abuse. And they won't mildew and curl like the paper ones left aboard! The charts cover a limited scope in excellent detail, so are great for day-sailing and fishing, but extended trips will require supplementary charts. That's where the chartbook kit comes in. These folding charts make quick reference easy. Fold them up to the area you need now, and stuff it in your pfd in any weather. A few of these for critical areas means you keep the paper charts shipshape and dry below decks while it's raining or blowing a gale. Saves money in the long run.
One word of caution, they do blow overboard, so hang on to em!