The GM seal changed over they years, possibly supplier rather than improvements, but even while it was rubber, latex coated, hollow in different areas, solid sponge or rope core, it still had the same part number, often a couple depending on length of seal. As in, it still didn't tell you what version you were getting, or what was used during production line use.
Hollow seals have benefits but haven't seen anyone actually give feedback on a comparison to the regular rubber seal they are still slamming to try and close.
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