According to internal tests, the Contact Sealing Frame from Thermal Grizzly is compatible with AMD's Ryzen 9000 and 9000X3D processors, which also includes the AMD Ryzen 7 9800X3D CPU. It should therefore work with the AMD Ryzen 7 9800X3D CPU.

This is a foam frame that protects the electronic components around the processor's heat spreader. This prevents a possible short circuit when using liquid metal. With normal (non-conductive) thermal paste, this part is not necessary. But it doesn't do any harm either...