Regardless of Feature Size (RFS)

The default: the tolerance applies as stated at any produced size — no bonus, no symbol in the frame.

Definition

Regardless of feature size (RFS) means the geometric tolerance applies at its stated value no matter what size the feature is produced at. A ⌖ ⌀0.5 A B C frame without any material modifier keeps its 0.5 zone whether the hole comes out at its minimum, its maximum, or anywhere between — the produced size has no effect on the tolerance. There is no bonus, ever: the zone is what the frame says it is.

RFS is the default — that's the part people miss

Since the 1994 revision of ASME Y14.5, RFS is the implied default for every tolerance that could otherwise take a material modifier. The old Ⓢ symbol was deleted; its absence in a modern frame does not mean anything special — it means RFS. ISO works the same way. The common confusion runs the other direction: a frame that does not show Ⓜ or Ⓛ is often assumed to be an MMC callout, when it is in fact the plain default. If a designer wants MMC they must write Ⓜ; nothing is implied by silence except RFS.

No bonus — and no functional gauge

Because the zone never grows, there is no MMC boundary to build a gauge to. A fixed functional gauge checks the virtual condition — an MMC concept — so an RFS callout cannot be functionally gauged. Verification needs variable measurement: the feature's location is measured against the tolerance at its actual size. For runout, concentricity, symmetry, and surface-applied orientation or form controls, RFS is not just the default but the only possibility — those controls never take a material modifier at all.

RFS vs. MMC vs. LMC

• Assembly clearance drives the design → MMC: the worst case sits at maximum material and the zone grows from there
• Material retention drives the design → LMC: the worst case sits at least material
• The tolerance must hold at every size — or the size dependence is itself unwanted → RFS, the plain default
• The control cannot take a modifier at all (runout, concentricity, symmetry, surface form/orientation) → RFS, automatically

Measurement

CMM coordinate measurement — measure the location at the feature's actual size and judge it directly against the stated tolerance. The standard approach, and the only one for RFS callouts.

Indicator setups — for runout and similar rotation-based checks, the RFS requirement is inherent to the measurement: the indicator reads the surface directly, with no size-dependent adjustment possible.

When to use it

• Features whose location must hold at any produced size — where bonus tolerance would let function degrade
• Runout, concentricity, symmetry, and surface-applied controls, where a modifier is not permitted
• Low-volume work verified by CMM, where the MMC boundary buys nothing and a gauge would never be built anyway
• Mating pairs where the size and location are functionally independent