I have a solid, convert to surfaces… and gave me 6 surfaces.

I need to know if is circle or not.

And after, isolate both (2) curves that is in down surface, but EXTERNAL CURVES.

The image below show all my 4 curves that is in the surface down.

I want isolate just the purple and blue, because are external.

Sorry Jacob, I understood 1 and 2… but step 3 and 4 not.

Step 3 starts with a closed polycurve. Wire that into a Curve.PointAtParameter node, pulling 11 evenly spaced parameter values. I recommended using a code block to assemble the values - this is the `0..1..#11`

bit. Then use this node to generate a circle through the resulting points: Dynamo Dictionary.

Once you ha e the circle you can ask the distance from the points generated by the curve.pointatparameter node to the circle, and compare the area (area of a circle = pi*r*r) to the area of the surface.