For someone who only bowls every once in a while, for medium heavy conditions, I would suggest either a Slash or a Freak A Zoid. You won't spend as much money as the high performance line, and those balls will be a logical step up from your Nitro. You don't want to get something that is very different from your current ball. You could easily get discouraged, and that is not what anyone wants.
Clint
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Clint Daley-Owner
Lets Go Bowling Daley
Salem, Ohio 44460
TRACK ADVISORY PRO SHOP STAFF