Thermostat neck from Billet Technologies

First question if it's an O-ring the manufacturer knows it needs to be down flat and the o rng is what makes it seal. So I can be taken on and off without leak and no mess. Assuming lol the manifold has a nice sealing surface. I myself have no experience with this perfect world scenario.
I used a dollar gasket and "the right stuff" and never seen a leak there. I'm sure I have the crome junk one.