Centurion porcelain-on-steel markerboards are the hardest marker surface available, and will resist scratching, denting, or staining. Dry erase boards have a steel substrate so these are also magnetic surfaces. Fifty-year product warranty. Specifications. All boards come with one eraser and one or four markers, as noted below. Aluminum frame, 1 marker. Dimension - 2 x 3 in.