I just went to Summit and here is how they list:

Fel-Pro
Port Ht 1.33
Port Width 1.84

Ultra Seal
Ht 1.48
Wt 1.78

That's a pretty substantial difference in height. These Mr Gasket port holes seem too large in the height direction when laying them down on the stock manifold. There was almost NO material covering the top of all of the ports at all. You can see the carbon lines on the manifold along the tops of each port....and it's right at (or maybe past!) the edge of the ports. Not Good.

BTW: I have used this mani for 5 or 6 years....this is really the first time I've had serious issues with it. Laying a straight edge over the ports, it sure seems pretty straight to me. I didnt get the feeler gauges out, but eyeing it up, I can't say this POS is warped to a point that it wouldn't give me a decent seal.