Tips on shopping for crappy screen protectors?

I’m shopping for a crappy screen protector, and I’m wondering what features or brands to look for. Maybe they’re pretty much all the same, I don’t know.

What features are most important when shopping for a crappy tempered glass screen protector?

My phone is probably worth about $30 at this point and I have a backup phone, so I’m not interested in investing a ton into protecting it. (If there even are fancy ones.)