What thermal pad to use?

Does anyone know the thickness of the Slim PS2's (in my case 79xxx and 90xxx) thermal pad?
I'm looking for replacements as the ones that my consoles have are really dirty and I'd like to put in new ones.
Thanks!

Edit: I have 1,5mm ones but comparing to the ones in my console are pretty thick, I'm thinking on getting 0,5mm ones.