An off-register is the misalignment of two o-ring halves, caused by the lateral shift of one mold cavity plate relative to the other. A mismatch occurs when the cross sectional radius of one half ring is unequal to that of the other half, caused by a dimensional difference in the mold halves.

Specification Max Allowable Off-Register Length (inches)** Max Allowable Mismatch Length (inches)**
AS708* .002 .001
ISO 3601-3 CS .0016 .0016
AS871 .003 .003
ISO 3601-3 S, DIN 3771 S .0031 .0031
ISO 3601-3 N, DIN 3771 N .0031 .0031
MIL-STD-413C .003 .003
RMA OR-1 A .003 .003
RMA OR-1 B .003 .003
Note: A 0.040 to 0.060 cross section has an off-register limit 0.002, and a 0.070 to 0.275 cross section has a limit of 0.003.
** Data above shows maximum allowable Length of Mismatch/Off-Register assuming an O-ring cross sectional diameter between 0 and .1 inches.

Off-Register / Mismatch diagram

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