The Size command (Insert | Dimension | Size) facilitates computing and reporting of local and global sizes per the ISO 14405-1 or ASME Y14.5 standards. The ISO 14405-1 and the ASME Y14.5 standards define local and global actual sizes.
For ASME Y14.5, the allowed features are cylinders, opposed parallel planes (also known as 3D widths), spheres, circles (cylinder cross sections), 2D widths (3D width cross sections). ASME Y14.5 defines the unrelated actual mating envelope and the local size.
For ISO 14405-1, the allowed features are cylinders, 3D widths, and their cross sections. Over twenty modifiers are defined in ISO 14405-1. You can combine these modifiers in various ways to create a specification operator for size. Separate specification operators are allowed for the upper and lower size limits. This means that thousands of different kinds of size calculations exist.
More:
To Dimension a Feature Using the SIZE Option
Supported ISO 14405-1 Modifiers