If you thought you'd be happy with what they sent you then I would keep it, but still make the company aware of the mistake.
Since you don't sound like you are bowling on lanes would allow you to use a strong ball like the Virtual Gravity, then I would get ahold of the company and ask them to send you the correct ball that you bought. If they can't, then demand and refund and consider taking your business elsewhere in the future.
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University at Albany 2007
-Let's Go Danes-
ROTO GRIP - King of Them All
STORM - The Bowlers Company