Precision 5520 Xeon E3-1505M v5 - Thermal Pads

Hi all,

I want to change the thermal pads for the VRAM chips under the notebook`s heat sink, and I would like to know the size and the optimum conductivity of the pads.

Looked everywhere on the internet, but I did not find the right info about those pads and I do not want to mess something up by changing them with something inappropriate.