The Otterbox Defender iPhone Case is the cadillac of iPhone cases from what I am told. I have been told repeatedly at the Apple store that if you want the highest level of protection for your iPhone, the Otterbox is the way to go.
They are currently on sale at Amazon for up to 65% off. The Otterbox Defender for iPhone 4/4s in Ocean/Night Blue is just $17.50 (65% off) and they have several other colors and versions for the iPhone 4/4s and iPhone 5 seriously discounted right now. Click here to see all the Otterbox cases I found on sale with free Prime shipping.
Shipping is free with Amazon Prime or with a qualifying $25 purchase.
Please remember: Amazon prices can change very quickly. Please verify that the price is the same as what I post before purchasing. As of 2/7/13 at 1:36 PM, this listed price was accurate.
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