https://www.applerubber.com/seal-design-guide/oring-basics/parting-line-projection/
Parting Line Projection - Seal Design Guide | Apple Rubber Products
Parting line projection is a continuous ridge of material located on the parting line at the ID and OD of the o-ring.
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https://www.applerubber.com/seal-design-guide/oring-basics/summary/
O-Ring Basics Summary - Seal Design Guide | Apple Rubber Products
Elastomer seals are unlike any other materials that design engineers confront.
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