Does any one know that clear plastic phone companys put on a new phone?

will it ruin my samsung impression phone if i leave that on there with a case over it? will it leaves bubble stains on the screen if i take it off eventually? (the case goes over the screen)Does any one know that clear plastic phone companys put on a new phone?
Go to Ebay and type in Samsung Impression Screen Protector...these are even better than the ones from Samsung (or any other company) cuz they are of a harder material (not all flimsy like the one you now have)...they stick to the screen by static, and it does not ruin it at all...i am currently using it on my Samsung Eternity...and they're dirt cheap w/ free shipping, like $4 or less...

rashes