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I have the Incase snap-on smoke case. It does a pretty decent job at protecting the back part, but the front is left unattended much. My old 3GS Incase slide case sorta made the case thicker on the top part as to the screen be lifted by 1-2 cm from the ground.
 
here are my top 3

Incase snap-on smoke case
Incase snap-on clear case
Belkin Shield Micra

i cant decide which of these to get
 
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