Symbol: 
Definition:
The Spherical Radius symbol is a variant of the Radius symbol, with the letter “S” placed in front of the Radius symbol. The Spherical Radius symbol is used to indicate the radius of a spherical, rather than circular, feature.
Application:
When dimensioning a spherical feature using its radius, the spherical radius symbol, “SR,” is placed in front of the size dimension, as shown below. In this example, the feature has a spherical radius of 1.25.
Feature with a Spherical Radius Dimension
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