Or do you have to use a new one every time you pull the head. For that matter what about stock head gaskets?

 

for stock headgaskets you are to replace them ever time you pull the head, not sure about cometic.

 

you're not supposed to use any gasket after its been crushed. especially a head gasket because oil and coolant gets between the layers when you pull the head off. earl and ninesecrx reused a cometic head gasket on their last engine and they eventually discovered it was leaking. ask them about it.

 

Typically copper gaskets are supposed to be re-usable for a couple of times though.