Foreign material accounts for any contamination present or any indentation left by the removal of a contaminant.

Specification Max Allowable Off-Register Length (inches)** Max Allowable Mismatch Length (inches)**
AS708* 0 0
ISO 3601-3 CS .0051 (Indentation after removal) .0031
AS871 .003 (Indentation after removal) .002 (Indentation after removal)
ISO 3601-3 S, DIN 3771 S .0059 .0031
ISO 3601-3 N, DIN 3771 N .0236 .0031
MIL-STD-413C 0 0 0
RMA OR-1 A 0 0
RMA OR-1 B .005 .003
Note: No tool marks or defects discernible to the naked eye are permitted.
The data above shows the maximum allowable width and depth of contaminant/foreign material/indentation assuming an o-ring cross sectional diameter is between 0 and 0.1 inches.

Foreign Material / Inclusions diagram

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