The moment you would go out shopping for a suitable screen protector you may come across different phrases used such as military-grade protection, 9H hardness, and so on.
9H hardness refers to the ability of the screen guard not to be scratched with a 9H pencil, which is one of the toughest pencils ever made. The best type is one that would protect against cracks and scratches without leaving behind sticky fingerprints on the surface.
The best one should also be easy to apply on the device’s surface. Overall, what matters besides everything else is the sturdiness of the one you buy.