Hey Boss, It's not the cover stock hardness, it's the hardness of the particle they add to the cover stock! Just like the hardness of the cores and what they put inside of them have changed. Lane Masters told me before they went out of business that changed to the carbon particle to try to match the diamond particle as close as possible. Just my $.02, Bruce
From USBC website:
Material
1. The ball shall be constructed of solid material i.e., no liquids and without voids in its interior.
2. Any material added to or included in the coverstock shall be equally distributed throughout the
entire coverstock of the ball, except for materials used in logos and other required markings.
3. The density of any piece/component in a ball (e.g. core, coverstock, weight block, etc.) shall
not exceed 3.80 g/mL (i.e., no pure metals or high density materials).
4. Following approval of the ball, the introduction of substances that are not comparable to the
original material used in manufacturing of a bowling ball is prohibited. Likewise, altering a
bowling ball in any way so as to increase its weight or cause it to be off balance outside the
specifications is prohibited.