Thermal Pad thickness recommendations?

I could really use some advice here.
I'm looking to order some Thermal Pads for an HP repair guide, but I'm stuck on which thickness to go with. Does the specific material actually matter?
The ones currently inside my laptop are this light baby blue, kind of like silicone rubber. I only need one single pad for this setup.😁
I've been browsing this link:
https://www.ebay.co.uk/sch/i.html?_f...p2045573.m1684

What’s the point of this thing anyway? Like, what's the actual use case here? Where does it even come into play... especially if you're just sitting there with one in your lap?

Sent from my ASUS_Z00AD via Tapatalk

I was swapping out my thermal paste. A little blue rubber band 😁 fell out during the process, and I honestly thought, "Whatever," and just tossed it. 😁
Then I noticed my laptop was running way hotter than usual 😁. After some digging online, I realized how much that little thing actually matters.

These aren't my photos, though. Just grabbed them from the web.