Anker KARAPAX iPhone X Screen Protector
I started keeping tempered glass on my iPhone when I got the iPhone 7 Plus. While the iPhone screen is very durable, I like an added measure of protection. For my iPhone X, I got the Anker KARAPAX iPhone X Screen Protector. It's very similar to other products on the market, but the installation process is the reason I recommend it. It includes an alignment frame that assists with putting the protector in the right place. The end result is a much smoother end result.
You can buy a 2-pack on Amazon for $7.99.