Feature
The general term applied to a physical portion of a part, such as a surface, pin, tab, hole, or slot or its representation on drawings, models or in digital data files.
Feature of size
Regular Feature of Size
Cylindrical or spherical surface or a circular element or a set of two opposed parallel elements or opposed parallel surfaces, each of which is associated with a directly toleranced dimension
Irregular Feature of Size
Type A) A directly toleranced feature or collection of features that may contain or be contained by an actual mating envelope which is a sphere, cylinder or pair of parallel planes.
Irregular Feature of Size
Type B) A directly toleranced feature or collection of features that may contain or be contained by an actual mating envelope other than a sphere, cylinder or pair of parallel planes