XC Base is a base wax with the purpose of getting the kickwax used to stay on the ski. Used in rough hard snow that wears on the kickwax. This is what the classic skier needs.
BASE kickwax works like a zipper between the coating on the ski and the selected kickwax, which means that you lock the kickwax and then increase the wear resistance. Used as a base for all kickwax when the tracks requires it.