Tolerance indication required for reference or auxiliary dimension
Reference and auxiliary dimensions typically do not require a tolerance indication.
However, a tolerance is required under the following conditions:
The associated feature has a geometric tolerance applied at maximum or least material condition (e.g., Ⓜ or Ⓛ)
The associated datum feature is referenced at maximum or least material boundary (e.g., Ⓜ or Ⓛ)