The Stealth Extreme Lite (iPhone 5 and 5s; $35) adds a 0.2mm thick pane of glass on top of your iPhone's screen to protect it from bumps and scratches without significantly impacting its optical qualities—or your ability to use the handset's touch interface.
The glass is tempered to prevent it from shattering, and treated using an aggressive chemical process that, according to the manufacturer, makes it harder than steel (though, presumably, a bit more transparent).
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