The Slate Blue was for heavy oil.
The Blue Denim used the same cover as the Riot Zone and the Lane#1 Pro Purple. It was meant for medium oil, but can be stretched down to medium-light or up to medium-heavy depending on drilling and bowler's revs. This was THE longest lasting particle cover made by Brunswick, as far as I know. I am still using my Riot Zone - can't kill it with a stick, so to speak.
I think the Blue Denim would stand toe to toe in carrying ability and utility with 95% of the balls out there now! I know my Riot Zone does.
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"...for advice is a dangerous gift, even from the wise to the wise...."
J. R. R. Tolkien