In GD&T, maximum material condition (MMC) refers to a feature-of-size that contains the greatest amount of material, yet remains within its tolerance zone. Some examples of MMC include:
- Largest pin diameter
- Smallest hole size
In contrast, least material condition (LMC) refers to a feature of size containing the least amount of material, yet remains within its tolerance zone:
- Smallest pin diameter
- Largest hole size
The MMC and LMC symbols are, respectively, the letter M or L inside of a circle. An example use of the MMC symbol is shown below. The boxed symbols can be read “the position of these two holes may vary within a cylindrical tolerance zone of 0.1 relative to datums A, B, and C when the holes are at their maximum material condition”. In this case, the maximum material condition for the holes would be at 2.5, or the smallest hole. If the holes were not at their MMC the GD&T tolerance would be given bonus tolerance, effectively increasing the position tolerance of the holes.