Most of the older model Pressurements and SI deadweight testers and comparators have bonded seals on the TEST ports. See the manual or handbook for your model for more details, and/or search the Deadweight Testers section of our Online Knowledge Base for more information (seal kits, old manuals, handbooks, etc.)
If you have a current model that uses o-rings instead of bonded seals see this article, Deadweight TEST port o-rings (current models, and comparators)
This images below are from deadweight tester manual (left) and comparator manual (right). The top of the TEST port has an inside diameter of 13.5 mm (0.53 inch). Current models use an o-ring and have a smaller inside diameter of 9.4 mm (0.37 inch).
Items 28 (left) and 26 (right) are the same and are old part number B1066 or P101066. The current part number is here,
Part Number: 3917960
Desc :P101066,BONDED SEAL [PP45-4] [TEST STATION]
Here is an image of a typical bonded seal.
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