Symbol: 
Definition:
The Spherical Diameter symbol is a variant of the Diameter symbol, with the letter “S” placed in front of the Diameter symbol. The Spherical Diameter symbol indicates that the feature being dimensioned is spherical, rather than circular.
Application:
To dimension a spherical feature using diameter, the spherical diameter symbol is placed in front of the size dimension, as shown below. The part in this example has a spherical diameter of 3.00.
Feature with a Spherical Diameter Dimension
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