The "sphericity" of the Lambda's Grade 25 ruby is 25 millionths of an inch. Take an inch. Divide it into one million (1,000,000) slices. The amount of error is less than 25 slices…out of a million. The majority of machined parts are manufactured to within about 0.001 inches. I created the chart below to make blowing your mind easier on your brain.

Below is an electron micro-graph that will give you a reasonable comparison between a metal “machined” surface and the surface of an instrument ruby. The image on the left is the ground edge of a razor blade. This is probably a much smoother finish that you will see with machining. However, compared to the surface of a ruby sphere at the same scale, it looks like the Grand Canyon.

Yes, I know that's not "perfectly" round, but it makes for good reading right?