Seals for the variable volume are part of the standard P3800 seal kit with details in this article (as well as info on the intensifier seals):
P3800 Deadweight Tester Intensifier Seals
Circled below are the seals from the standard 4105694 seal kit that should be purchased. To place order can ask for our Orders group by calling +1.877.355.3225 or go through orders@flukecal.com.
Further info:
Screw Assembly:
Washers:
Rambler:
Below is several diagrams for further detail on the assembly and related parts:
