The Kodiak iGlass Shield Tempered Glass Screen Protector is the best way to protect your investment. Unlike those gaudy bubble-ridden film protectors (we've all been there), this is actual glass that is self-adhesive and blends seamlessly to your device.
No bubbles. No hazy display. No plastic feel.
Not only does it keep your device looking fresh, it adds durability as well. In the likely case that you drop your phone, the tempered glass will do its best to maintain the rigidity of your device so your screen is safe. The anti-shatter film contains the glass into harmless dull bits similar to an automotive windshield, potentially saving you hundreds of dollars in replacing a screen or phone.
Measuring only 0.3mm, you'll hardly know it's there. And better yet, you won't have any issues using it with a phone case or cover. It has a hardness rating of 8H (think topaz or cubic zirconia), and an oleophobic coating that repels dirt, oil, fingerprints and maybe even telemarketers.