Get a free Invisible Shield 4fix case if you purchased your iPhone 4 from Best Buy / Best Buy Mobile or you are a Best Buy Reward Zone member. It is pretty to sign up for the reward program at any store. The official Best Buy name for the product you'll be getting is the Zagg Side Shield, which would cost you $9.99 otherwise. Seems like a nice promotion to get you into the store to purchase other products and accessories. See Zagg's invisble shield web site for the full product review.
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