MMC, LMC, and RFS explain how a geometric tolerance relates to the actual size of a feature of size. These modifiers matter most for holes, pins, shafts, and slots where assembly clearance, wall thickness, or functional fit depends on both size and location.
Maximum material condition (MMC)
MMC is the feature size containing the most material: the smallest permitted hole or the largest permitted shaft. When MMC modifies a geometric tolerance, the stated tolerance applies at that size. As a hole gets larger or a shaft gets smaller, it can gain bonus geometric tolerance.
Least material condition (LMC)
LMC is the feature size containing the least material: the largest permitted hole or the smallest permitted shaft. It is useful when minimum remaining material is the functional concern, such as preserving wall thickness near a hole. Bonus tolerance can be gained as the feature moves toward more material.
Regardless of feature size (RFS)
RFS means the stated geometric tolerance stays the same at every allowed feature size. It is the common default when no MMC or LMC modifier follows the tolerance. RFS is useful when the geometry itself must stay controlled independently of feature size.
Bonus tolerance at MMC
A hole with a 10.00–10.20 size limit and a 0.20 position tolerance at MMC has 0.20 position tolerance when the hole is 10.00. If the actual hole measures 10.10, it gains 0.10 of bonus tolerance for a total of 0.30. Read the MMC guide, LMC guide, and RFS guide for more detail.
Frequently asked questions
MMC vs. LMC vs. RFS in GD&T: Material Condition Modifiers Explained FAQ
What is MMC in GD&T?
MMC is maximum material condition: the smallest hole or largest shaft size within its limits.
What is bonus tolerance?
Bonus tolerance is the additional geometric tolerance gained when a feature departs from its material-condition limit, when MMC or LMC applies.
Is RFS the same as no tolerance?
No. RFS means the stated geometric tolerance applies at every allowed feature size. The size requirement still applies as well.
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