I recommend Flolab screen protectors, they're not cheap, but not too expensive either (20$). Quality is great for the iPhone screen protectors and they have lifetime warranty, if you break the screen protector, they'll give you a free one you just pay the shipping fee.

I’ve used them on all my iPhones and all my friends and family use them too. I had no problem with the warranty either, it's an automated process you don't have to wait for someone to process it.