How to measure Intake Manifold Height

Anybody knows how Edlebrock measures Intake Manifold Height?

Is it from the top of the base or from the bottom? Or is the measurement based on how it sits in the block? If so where is the reference point?

7576 Air Gap 5.35”
2176 Performer 4.63”
7176 RPM. 5.35”
Author: admin